Nope. You haven't proven anything, lol. It remains unstated what effect it has on their weapons. We do know that the Warbird was compromised to the degree that it was a one way mission and it was a compromised Warbird that attacked the Enterprise causing significant damage.[
The compromised Warbird briefly attacked a full shielded Enterprise as a deterrent and went off to chase down Tin Man. The Enterprise was significantly damaged because of this. It's pretty obvious that the Warbird has an edge on a Galaxy class ship at least during the TNG run.-[
That might depend on the context:
WORF: Romulan warbird closing. They are arming main disruptors, Captain.
PICARD: Go to Red Alert. Shields to maximum.
RIKER: Arm photon torpedoes and stand by, Mister Worf.
WORF: Aye, sir.
RIKER: I thought you said the Enterprise was faster than this Romulan.
DATA: In fact, we are, Commander. However
PICARD: Evasive, Mister Crusher. Hailing frequencies.
TAM: I guarantee that they don't want to talk to you, Captain.
(Weapons hit, and the lights dim. The Romulan makes a strafing run then heads for the star)
WORF: The Romulan has passed us.
PICARD: Damage report.
WORF: Casualties reported. Seventy percent loss to the shields.
TAM: Their attack on us was incidental, Captain.
PICARD: Incidental?
TAM: Yes. To delay us.
DATA: Captain, it would appear that the Romulan's intent is to contact Tin Man first, at any cost. According to my sensor readings, the warbird has exceeded maximum engine output by thirty percent. They seem to have irreparable damage to their warp coils.
RIKER: So they kept up with us by sacrificing their ability to re-enter Romulan space.
The Warbird's disruptors managed to deplete the Enterprise-D shields by 70% in that attack... but given that the Romulans overloaded their engines in the process, its possible they did something similar to their weapons. As mentioned by Data, it was a delaying tactic.
If the Warbird really had the capacity to destroy the Enterprise-D in a few shots... you would think they would do that.
But then again, the Romulans DO use a forced quantum singularity as a power source... I wonder why the Federation doesn't use this kind of technology as it seems more efficient than using M/AM generation?
The Federation should be more advanced after all given it combines almost 150 member worlds by that time who share knowledge and resources - but they also do share various scientific findings with other species - still, if it occurred to the Romulans, then why not the Federation too?
Apart from that, There were 2 Romulan Warbirds that faced off the Enterprise-D in The Defector episode with Admiral Jarok.
Anyway, when the Enterprise crossed the neutral zone, it made sure to have several K'Vort class Birds of Prey with them.
WORF: Two Romulan warships uncloaking. Coordinates
(He's interrupted by impacts to the shields)
WORF: Shields holding.
RIKER: Damage?
LAFORGE [OC]: Minor damage in the secondary hull.
[Engineering]
LAFORGE: Power transfer fields may be pinched off.
[Bridge]
LAFORGE [OC]: I'm working on it.
WORF: Captain!
PICARD: Not yet, Mister Worf. This is just a tap on the shoulder, or we wouldn't be here talking about it.
So, on one hand, the Romulan attack did nothing of note to the shields, and on the other, Picard says its a 'tap on the shoulder' - probably because both ships didn't fire continuously on the Enterprise until it was destroyed.
Other episodes, (especially of note would be the one with Deanna on board a Romulan Warbird pretending to be a Tal Shiar operative) indicate that attacking the Enterprise with its shields on would not be a particularly clever thing to do.
They usually wait for an opening to present itself so they can deal a killing blow.
Otherwise, if the Romulans were more powerful, you'd think they would have beaten the Federation before this long and wouldn't engage in prolonged coy stunts.
Or, at the very least, the Romulans might have taken advantage of the Federation by attacking it when the Dominion attacked (Granted, they stole the Prometheus, and might have been successful if Voyager's EMH hadn't intervened - you're welcome Starfleet - a lone EMH from a starship 60 000 Ly's away managed to bring back your stolen ship).
How the heck did the Romulans managed to get a hold of the Prometheus in the first place?
The ship was supposedly 'top secret' and only 10 people in the entire SF knew how to operate it (which suggests high levels of automation - finally).
But for the Prometheus to be stolen by several Romulans in the middle of the Dominion War?
That's... unlikely.