Romulan Warbird

[Deks]

Just because Nemesis is the only time it showed up, doesn't mean it's brand spanking new.

The NCC-1701 was after all, 20 years old when James T. Kirk first hit the TV screen.

Point taken ... however the design seems more advanced in comparison to the TNG era show.
Then again ... I don't discount the possibility of the design being actually older than newer since we witnessed very retro type designs even on Enterprise as far as the Klingons go (the Raptor being a notable example).

Although ... the Valdore was referred in the movie as a Romulan Warbird.
If that is the case ... then it's quite possible that it is something akin to the Romulan's response to SF's Sovereign class?

 

[Herkimer Jitty]

The Valdore seemed to be more of a disruptor-focused ship, which would be an odd counter to the "LOL TORPEDOZ" armament of the Sovereign.

 

[Deks]

Well, to be frank, the Sovereign made an appearance (from our perspective) about 7 years prior to when the Valdore did.
The Enterprise-E underwent retrofitting after Insurrection events, and those changes involved potential additions of the decks and torpedo launchers ... the decks additions and slight changes in design would likely be doable on such a scale especially if SF ships are modular.