the phaser beam penetrated straight through the ship, causing massive internal damage and/or killing most of the crew
...But not by the Wrath of Khan mechanism, because that one involved actual physical cuts in the hull. If the entire
Excalibur were covered in such cuts, she'd be torn apart.
TWOK however is different in that they were low-powered phasers at point-blank range.
We've seen full phasers at transporter range (which would be 30,000km or under) at an unshield Klingon Battlecruiser and 2 double hits resulted in its destruction.
So full phasers beyond transporter range, say in the medium to long range at an unshielded Excalibur with 2 double hits could result in external scarring damage that we can't make out due to distance (although in later scene we see the ship's structure bent up since it was a re-use of the Constellation). So we do know that the ship's structure did suffer damage.
Granted, it's probably different phaser technologies at work though.
Is it "phaser technologies" at all, when a
power coupling sends the burst? We could say that M5 hurt a comparable power coupling that then sent a deadly burst from within the
Excalibur, but that's not something Kirk could discern from looking at M5 firing.
PARIS: I need you to get the computer to block the discharge from the
backup phaser power couplings.
It was the backup phaser energy that overloaded into the ship
Although I was arguing that Kirk probably knew that those types of phaser hits on the Excalibur would've been lethal.
As a former weapons officer, he'd probably be extra familiar with phaser capabilities...
Gotta nitpick this one: him crewing a "phaser station" in "Obsession" was related to firing at the vampire cloud, which would probably involve hand phasers rather than ship phasers. He might be a weapons officer, or he might be a security goon overseeing a major planetside operation from a hilltop fire base. But the point about Kirk knowing his way around phasers stands.
McCoy's dialogue puts Kirk at a phaser station and mentions Kirk's ship. The attack killed 200 crewman. So, it is possible that somehow half the crew was on the planet below vacationing when attacked, it doesn't quite make sense since Kirk was already manning the phaser station thus the ship was on some kind of alert.
MCCOY: Am I? I was speaking of Lieutenant James T. Kirk of the starship Farragut. Eleven years ago, you were the young officer at the phaser station when something attacked. According to the tapes, this young Lieutenant Kirk insisted upon blaming himself.
KIRK: Because I delayed in firing at it.
MCCOY: You had a normal emotion. You were startled. You delayed firing for a grand total of perhaps two seconds.
KIRK: If I hadn't delayed, it would have been killed.
MCCOY: The ship's exec didn't seem to think so. His log entry was quite clear on the subject. Lieutenant Kirk is a fine young officer who performed with uncommon bravery.
KIRK: Don't you understand? It killed two hundred crewmen.
Kirk's expertise with phasers, shipwide and personal, still stands. He would know what kind of effect Enterprise's phasers would have on the unshielded Excalibur.
Well what other times have we seen a ship fire full phasers at medium to long range into another equivalent ship with shields down?
"The Wounded"? We didn't get the impression that there were
any casualties aboard the
Phoenix.
I did say "another equivalent ship"
Remember that in the beginning of same episode, a Cardassian warship opened fire at close range against an unshielded E-D and only did minor damage.
WORF: Minor damage to secondary hull before we put our shields up, sir. No casualties. Structural integrity intact.
The Cardassians don't really become an equivalent threat until they team up with the Dominion...