It's not the storyline stretching past Mania that's the problem, it's the fact that they're doing the screwing him angle month after month with the end of goal of winning the title nowhere in sight. Bryan winning the title doesn't make the Authority's attempts to bring him down obsolete, it just intensifies them even more and they'll stop at nothing to removing him as the face of the WWE. This time, instead of Bryan being screwed in the big important matches, the roles are reversed and he overcomes the odds.
Do you honestly think though that waiting just that extra month will make things better / more special than them just biting the bullet and having him winning the title at the dirty 30 all the while getting that WrestleMania moment that all the superstars seem to talk about?
Also, I don't think the not being able to wait part isn't true. I know for me at least and i'm pretty sure the majority on here believed that prior to Batista's return he was winning the title at Mania so were fine in waiting in that long. To me it just feels like the Ryback situation they had when he was facing Punk for the title where he probably should have gotten the title but because they'd already made promises elsewhere to Punk/Rock/Cena they had to keep it away from him and ultimately he hasn't been the same since. You figure in that when Batista gets the title he will presumably hold it for a good 3/4 months and possibly drop it at SummerSlam (Just a guess, know idea what his schedule is) so how do they go about keeping the fans interested in Bryan again as they continue to screw him out of yet more title matches?