You make it sound like Punk got his long reign because of his ego, more like WWE or The Rock (who people wants to give credit to) wanted Punk to be the longest champ. Predictability when facing midcarders is obviously not his fault since no way guys like Ziggler, Jericho and Bryan deserve to win the title in his hottest time of his career. He lost a lot already and WWE plan was to have a long reign, if you're a casual fan you wouldn't know when he will lose it since they don't read rumors/spoilers like you do. To the casual people thought he will lose against Cena and Ryback. Despite you saying he got shit load of air time when it doesn't really matter, he had great segments with Jericho, Foley, JR, Bryan, Cena, Vince, Lawler, Flair, Rock, etc. And ever since he turned heel it was entertaining. So he didn't really need to shoot he did his best with what he had. His booking sucked. His matches in this reign is what stands out the most since it's one of the top in ring title reign.
Yes, it was ego because ask yourself this: Who did Punk put over during that reign? Who gained? Punk himself. . .that's it. And this directly followed him gaining popularity by saying he wanted the guys who weren't getting a fair shake to get their shot. None of them did besides himself. So in the end, it was all about him both in kayfabe and in real life. Even when Punk dropped the title, they booked that fued and especially the match WAYYYYYYYYYY in favor of CM Punk. They booked The Rock like a random jobber until the final two minutes. The Rock chose that? Not CM Punk? I don't think so. Punk's reign may have been mildly extended because of Rock, but it was already longer than it should have been before he presumably (and allegedly) said anything about it.
What spoilers? The only spoilers there are are for Smackdown where Punk didn't wrestle. There are no PPV or fued spoilers on the internet to find. If you're referring to that phony dolphins guy, he only started to post that stuff after Punk's reign ended as far as I know.
I also don't read dirtsheets (which are typically purely speculative anyway). Punk's fued outcomes were just that obvious based on how strong WWE booked him and how weak WWE booked his opponent (to make Punk appear that much more superior).
The only times Punk even seemed to have a chance of losing were because of our own pre-judgements altering our perceptions; which were his matches against Cena. We figured well it's Cena, Punk's reign has gone on awhile, it must be ending now right? Aside from those, the reason Punk's reign was so predictable was because of how it started. His first 3-4 matches were "beating the odds", practically in handicap matches. If he doesn't lose there, he clearly isn't losing against a single opponent whom he's booked to completely dominate.
I agree that his booking sucked, but most likely for a different reason than you. I think his booking was bad because he was booked far too strongly while his opponents were booked far too weakly. His fued with Ryback is practically the only exception, and of course, that's the fued Punkfans hated the most at the time. Not coincidently either.
Punk was booked strong as fuck. He just couldn't make it interesting since he doesn't have Cena-level charisma. Cena pretty makes clipping his fingernails seem like a major event. The only things Punk ever did that seemed major events were title matches (major by itself), and breaking the 4th wall (also major by itself). He didn't make much in between that interesting. And I'm sorry, but that isn't the fault of the booking. He got more air time and stronger booking than anyone else on the roster, it's no excuse for why he didn't look good.