I never found any of them to be that lengthy.
The UC4 E3 Demo setpiece seemed longer than any set piece in the franchise, which is why I'm a little surprised people are claiming there's less of them. Unless ND somehow spilled the beans on the biggest set piece in the game, which is possible of course.
Either way, the set pieces didn't necessarily make the games good, they just fleshed out the package.
Arguably, UC3 had the best set pieces but the game itself was a huge letdown because they weren't integrated intelligently into the game, and the overall combat design and pacing was not up to snuff.
Having played the Beta, this is easily the best *playing* game ND has ever made. Sublime mechanics. So I know the gameplay is going to deliver. If they can manage to make a competently woven package of the other elements in the series, there's no way it can disappoint.