About 50% of the time I find him, he is bugged. Now, originally I thought this was just due to people pulling him to Valley of the Four Winds to bypass having to phase him, and somewhere in that process they get him stuck.
However, while fighting Scritch in Kun-Lai, where there is a really tight terrain, I had him evade out and reset (fortunately not completely bugging out) while using Going Bananas. Blizzard, you guys are the developers, and by no means am I telling you how to fix your game, but I like to offer solutions when I complain about a problem, so...
1. Remove Major Nanners from phasing, obviously you can't ban every single player who uses "clever use of game mechanics" to pull him out of phase, and let's be honest, taking the Hozen out of phase isn't going to really mess with a newcomer to the zone that much, especially if they aren't Level 90 yet.
2. Going Bananas needs to be looked at. This ability is pretty unstable in terms of bugging out a mob. I've seen it reset encounters, bug out mobs completely, and really mess up their path, when they land inside a steep hill and bounce all over the place trying to run back to you. I suggest making it target a player and giving them a couple seconds to jump out. Because honestly, right now the ability makes very little sense to begin with.
Thank you for your time,
A concerned Death Knight