Actually the biggest problem was the unexplainable Romulan decision to cross the neutral zone at the speed of warp 2?!
How the hell can you cross a region of space one light year wide when according to the TNG warp scale you are only going ten times the speed of light? Does Vulcan sit directly on the neutral zone border?
The Federation Concil could have spent untold weeks debating a response to the "eminent" invasion of Vulcan.
Unification Part II had many flaws
(One Edit) After watching the episode on youtube, the speed is given as warp one when crossing into the neutral zone and "low warp" when entering Federation space. Still bad writing considering it takes 8.5 hours to cross the neutral zone traveling warp 9.