Some classes are going to be stronger than others, there is just no way around that. We are not going to go down any slippery slopes here. Some classes, when played well, are just going to be op. What we should be looking at here when deciding if something op needs to be neutered is this:
a) how op is it compared to everyone else?
b) how much skill/setup does it take to use?
c) how much does it take to counter?
Both Feral FB and Guard are op compared to everyone else, take very little skill to use, and you can't really counter them. FB is one button and you are dead. Guard is... I mean you can't even dispel it. There is no skillful way to counter Guard. No cast to kick, nothing to anticipate and counter ahead of time. Your only option is to get in a position to burn it down. Yes, that can be done with coordination on voice between DPS, but that doesn't mean it's not OP
In big, balanced mid fights, you have to sync DPS to get a kill anyways. Having Guard on top of that, and you have a 30 second window otherwise it's just up again?
I don't think anything else in the bracket is quite at the same level as these two.