Well, let's be fair here, Whistler was just another PTB Seer. Cordy & Doyle never got the big picture either. Cordy even accidentally had Angel kill another Champion protecting a pregnant woman once...
Personally, I am a Bangel simply because Joss is a Bangel. So that aspect doesn't really throw me. Issue #34 is going to make or break the Buffyverse for me (Similar to what AndrewCrosset was saying about this one). If we get a sensible explanation, then I can go with this, otherwise, S8's ruined the franchise.
For me, I think I'm going to need it to be Cordy and/or Doyle who have convinced Angel to do this, because, regardless of how good a reason Angel has, it won't make sense to me if his source isn't a Higher Power who also happens to be his best friend.
Angel couldn't muster himself to kill Holtz after kidnapping Connor, stealing 17 years of his life, and brainwashing him. It won't be believable unless we see that Cordy came down from the Higher Plane showing Angel the future that would be if Angel didn't go on his killing spree.
I'm also wondering what the finale's going to be if Super Angel & Super Buffy are "sex buddies" again. The only enemy big enough for the two of them to reasonably fight would be Wolfram & Hart. And it would sure be odd if this turns into a mission from TPTB to combat W&H, because in that case this whole season of Buffy has been about resolving Angel plot-lines (which I doubt).