A paladin from my guild wanted me to ask about cleanse failing. On Teron and Reliquary he's had that problem. It actually will say "Cleanse Failed". He has it in a macro, so maybe that's it. I really am not too good with some of these newer macros so I can't help him.
/cast [target=mouseover,exists] Cleanse
I know this happens occassionally, but it seems to happen a LOT for him using this macro. When he switches to just a bound key, it's fine.
Same premise as is going on with spellsteal. Some type of "resist" is what it basically boils down to. It has something to do with the level of the debuff versus the level of the cleanser, and was largely responsible for the "buggy" rogue poisons prior to patch 2.1 when the level of the debuffer was essentially the level of the item, making rogues who used poisons on their ilvl 100+ weapons extremely resistant to cleanse attempts.
As far as Teron goes, we've had some weird issues with the stairs where people on the middle of them couldn't be dispelled by two different paladins five yards away down the stairs. I have no idea what the actual error was though and we havn't seen it since we moved people off the stairs.
I have noticed that I get more "You fail to remove [insert Curse name] from JoeShmoe" in BT/Hyjal than I ever got in pre-BC content.
Perhaps it's the old '32 Syndrome', where I'm simply looking for it, but on several occasions, I have failed to remove Grip during Archimonde several times in a row. That is to say, someone gets Grip, I attempt to remove it, while standing right on top of them, it fails, I try again, it fails, I try again, success!
The banshee curse in Hyjal is another one that comes to mind, where I can repeatedly fail to dispell it. No clue why it's happening with more frequency of late, though it is a tad annoying.
I've noticed that if someone beats me to a cleanse (by either dispelling or cleansing), often times I'll get an error of failing to cleanse so and so. Could that be what he had happening? More often than not it'll say nothing to dispell, however there is the odd time where I get the fail to cleanse line in the combat log.
I've given this some thought too - particularly in reference to Abolish/Cure Disease. Cure is the lower level one, and just perhaps might have a resist chance based on it's learned level, while Abolish is much cleaner generally.
I always thought, as a result, that in the Mage case we would finally get "Remove Curse" or "Remove Greater Curse" since all we have now is Remove Lesser Curse.
Hmm. Has anyone tested if spell hit or spell penetration (lol) gear helps?
Removing a level 73 debuff can't have the 17% miss chance that landing a harmful spell on a level 73 target can. Though it may be that most of the debuffs we've been suppose to remove were mostly level 70 (or 60 pre-BC) and the ones people are having trouble removing are >70.
Has anyone done testing concerning resist chance and pet spells, such as devour magic? I never trained past rank 2 devour magic, and I'm sure many other warlocks did the same thing (so their pets would not go out of mana chain-purging someone). I notice a high level of resists with my devour magic, and as such have had to set it to auto-cast, since reactive devouring is almost never an effective strategy.
I had always gone by the idea that it was based on caster or pet level, however I can attest to cure disease failing most of the time as well.