It hasn't been perfect, not even close overall to be perfectly honest, but one of the worst in history? Not by a long shot, not even in the top 20 worst title runs in WWE history.
Vince McMahon has a desire to make every heel champion that isn't some 250+ pound slab of muscle look vulnerable; like a lot of things, Vince takes it too far in that he makes the champion look too vulnerable and it's also a concept that, in my opinion, WWE makes far too frequent use of.
However, to be fair, people would complain about Rollins' run no matter what. If he's booked to come off as "too strong", if he was booked to come off as some walking incarnation of badass, some fans and writers alike will complain that Rollins doesn't cheat enough or that he isn't being enough of a heel. If he looks like some walking incarnation of badass. It's part of the same sort of thinking that causes some fans to declare that a guy is being buried if he loses a match, or that a heel looks weak if he does cheat, or that someone's being targeted by company officials because they get off on screwing people over. Some will complain if Rollins' run isn't EXACTLY what they want it to be or feel it should be; since there's no chance of such a gloriously perfect run from Rollins, or anyone else for that matter, it's just a setup for bitching to begin.If Rollins managed to remain champ all the way to WrestleMania, or even to the end of the year, look at how many would come to the forums complaining about him being champion for too long, yet many of those are the same fans who gripe about WWE playing hot potato with titles. Some are going to complain, are currently complaining or have complained just for the sake of having something to gripe about whether they mean it or not.