For defense, not offense. You said "offensive," and that is not correct.
Since Offensive would mean to attack an enemy, and weapon is that which does harm or damage, external of the purpose of Star Fleets bottom line, then describing these implements as Offensive is according with their uses. Furthering the point, Federation ships have "alot" of them.
The Tzenkethi and Cardassian conflicts were minor on the scale of the Federation as a whole. Remember, "The Wounded" established that the Cardassian war had been going on during the first two seasons of TNG, but those seasons clearly portrayed Starfleet as a peacetime organization sending out civilians and children on their ships, and portrayed Picard as an explorer who had little experience with taking life ("Conspiracy") and didn't consider war games a necessary or useful practice ("Peak Performance").
Officially there is no word on how long the Tzenkethi War proceeded and there is no mention of it in TNG yet Sisko was clearly involved along with Admiral Leyton.
According to Memory Alpha (who maybe correct or in error) the Cardassian War started in 2347. A treaty was established in 2367. More than 5 years of war. 19 years and what is described as numerous conflicts and skirmishes.
Clearly the Federation is such a vast civilization that a conflict on one border doesn't necessarily have a major effect on the rest of it. The only major, Federation-wide war we have any evidence for is the Dominion War.
The only major war proven is the Dominion War the other wars are expressed explicitly and somewhat implicit as to how serious they were. Evidence exist but somewhat contradictory to the scene and quite circumstantial. Piecing together the writers whims has always been problematic. I don't suggest there is any real continuity only a pretense at it.
Even aside from that, let's do the math. The Cardassian conflicts were from about 2355-67, on and off, and the Tzenkethi War was sometime during that same period. The Dominion War was 2373-5. Add a year for the conflict with the Klingons that preceded it, and we're talking only 15 years out of the century. And only the 2-3 years of the Dominion War constitute a major, Federation-wide war rather than an intermittent or localized border conflict. (Well, that and the Borg invasion of 2381, but that only lasted a couple of months and the final full-scale onslaught covered less than two days.)
According to my count nearly a Quarter Century of War. 19 years of Cardassian Conflict until the Treaty, 3 years of Dominion Conflict. One year of Klingon Conflict in the latter half of the century.
Included on top of that number is the Sheliak Treaty of Armens which implies a conflict (never stated explicitly)
A Ferengi Conflict that led to them entering into the Khitomer Accords.
And Despite the First Khitomer Accords a second Accords in the 24th century that implies heavily that without the self sacrifice of the Enterprise-C, 20 years before the Enterprise-D, that the Federation and Klingons were still in some sort of degenerating relationship. We're not given details. We can only speculate as to these being open conflict or some other sense... Tumultuous over lapping conflicts .
Exploration is a dangerous business. Look at how many Constitution-class ships or crews were lost between 2267-69 -- Constellation, Exeter, Intrepid, Defiant, Excalibur. None were lost during wartime.
For that matter, why assume that every possible registry number within a given interval was actually built? For instance, if the McGuffin class was NCC-4700s and they only built 13 of them, then there'd be no ships between NCC-4712 and NCC-4800, the prototype for the next class. So you may be overestimating the numbers.
Those ships represent only a hand full out of tens of thousands lost. If thousands of ships were lost I would rather describe that as fatal and not just dangerous.
As for the NCC's being blocked by class, I have no evidence to indulge in that particular conjecture. Rather DS9 heavily implies that every number is a contract vessel. As mentioned before it is factual that the Dominion had 30,000 ships between it's self and the Cardassian Union. With the Klingons only having 1200 and the visual evidence supports a greater number of Star Fleet ships in every single engagement over the Romulans. Voyager and DS9 also imply that prototype ships are sometimes non commissioned in the case of Prometheus and Defiant but their number still counts. The Excelsior implies that prototypes are given an official contract of construction being converted to NX to NCC which I've speculated means that the class has entered official production in numbers.
But I need something that implies that a running count is something other than a progressive increase, something from canon. Running counts depict progressive order. We do know there are consecutive ship registries, 1700, 1701, 1703. Intrepid suggest that NCC's are given chronologically not in blocks. Voyager is deduced to be the second ship of the class even though it's 56 units after Intrepid by the fact that she is the first ship to be tested in deep space. Other than the mere conjecture that not every number is a filled number which only serves the purpose of being incredulous, I've personally found no such evidence. Is there something that implies otherwise to you?
No, most Federation ships are explorers. You're making a mistake by limiting your thinking to combat-vessel analogies. There's nothing in "explore strange new worlds, seek out new life and new civilizations, boldly go where no one has gone before" about combat.
Because Combat and Exploration are not mutually exclusive of a starship's abilities I chose one aspect of focus to determine whether there abilities are more offensive or scientific. Aside from the mission statement and the Star Fleet bottom line I was only seeking to describe there abilities in a combat or non combat frame of reference. For instance a non combat ship like the Oberth has little to no offensive weapons and is dedicated (almost strictly) to scientific endeavors. There are other ships that imply the same such as the Steamrunner Norway and Sabre class. They all have less than Five phaser arrays which is a basic Star Fleet armament. Most of the StarFleet ships have 10 or more covering all arcs. That implies a priority of combat. The Luna class has prominent sensor packages. Ships that also have them are the Intrepid, Nova, Nebula and Galaxy. (strictly according to the hardpoints)
But I broke down classification explicitly on size/weapon ratio
Galaxy:
It's incredible size is not an offensive priority. That size serves non combat abilities, scientific laboratories , Colonization, Evacuation, diplomacy and luxury. (including an impressive full 360 sensor array)
Yet offensively it's more than well armed. 12 arrays and 3 cluster fire launchers. It's also quite fast.
The emphasis is Defender/ Combatant because it's size purpose dominates it's offensive purpose. or Explorer/Combatant
Intrepid
Intrepid on the other hand has far less space. It's not meant for luxury or diplomacy, colonization or evacuation purposes. It's hard points suggest that size is scientific.
Offensively it has more weapons than the Galaxy and nearly matched Defensive abilities. It's the fastest Federation ship aswell. It was described as quick and smart with a tactial sensor range of 15 lightyears which was far greater than Galaxy and better than any ship in the fleet. Intrepid is also highly manuverable for it's size.
There is an emphasis here on Combat with it's weapons and speed and yet a nearly equal role of exploration. I define it as a Combat/Defender or Combat/Explorer.
Defiant
It's size suggest limited space especially it's actual volumetric on the 120m ship most believe it to be. Limited scientific resources.
While it's armament suggest an extreme emphasis on forward offense with four canon and 2 launchers with other armaments depending on the episode. The ship is also extremely maneuverable
It's a Combat ship
Every Federation ship seems to fit this sort of classification much better than terms like Destroyer, battleship or frigate and it also properly fits the classification of "crusier" which is the common classification we've seen and heard in canon which defines as a detached (solitary) independent mission warship.
I've looked some definitions of Warship:
Warship: A combat
ship.
Warship: a government ship that is available for waging war
Warship: A warship is a ship that is built and primarily intended for combat. Warships are usually built in a completely different way than merchant ships. As well as being armed, warships are designed to withstand damage and are usually faster and more maneuverable than merchant ships. ...
Warship: Any ship built or armed for naval combat
So that is the schism between what Star Fleet says they are an what the ships abilities prove to be. It's also (apparently) the on going debate between fans as to Star Fleets mission between what they say and the impression that is given with their ships (who the klingons certainly doubt), their uniforms, rank and structure.
I don't think there is a schism. The ships are commonly warships but the purpose is defense of the Federation and it's allies and peaceful exploration while it's membership or attendance is by far for the majority of scientific endeavors which is why I think Star Fleet weaponry relies on a high degree of automation and thus do not require large crews like comparing the original enterprise of 288 meters and 400 crew to that of the real Enterprise with a crew of 5,800 at 344 meters.
Starfleet vessels are not warships
Says a Bajoran terrorist, with sarcasm dripping off her pretty lips. And Sisko
scowls and
ignores her.
Timo Saloniemi
hmm. I'm not sure if that how it was intended, Timo.
I took her surprise as genuine. Why do you think it was sarcastic?