turtsmcgurtstyrant used to be okay, the recent patches have made him useless though. deceiver is pretty gimmicky, they may have made it a bit better recently though, not sure. there's practically only one sentinel that is even remotely scary to play against and that's the streamer Raziel and even then as soon as you swoop in to pick somebody up, you don't have many options as to where you can go... it's almost always up in order to apply damage, which would get you killed instantly against good players. all the human classes are fairly even, even alchemist (although he would be ranked lowest)
Tyrant is decent at best. I didn't play this pre-the patches you speak of, so I can't compare. Against bad/unaware players, it's typically pretty easy, to be expected. Against better, or even decent players, I find it best to jump in, possibly quake and just leave. It is in no way smart to use the vanilla charge and lead fights against decent players. You're better off with the hit and run or just letting your reavers do their thing and come in after for a couple seconds, if it doesn't allow for me. It's more or less, right now, just a class I want to play because the abilities are fun. I am in no way convinced the class has any long term standing.
Deceiver is pointless, unless no one knows what they're doing. I have yet to run into a good deceiver.
In terms of the human side, Scout is stupidly easy so long as your team isn't terrible. Prophet is probably the all around best, in my opinion. I can't get into the Hunter, and the Alchemist is pretty boring aside from getting airshots that seem a lot more satisfying in this game.