I roll Warlock all the way. Like Galvatron said titan has better armor and their supers are pretty good, you can either pop a protective bubble around you where you take no damage or you get Thor's hammer and throw them at people or do this massive ground pound that destroys everything around you. the Hunter has either blade dancer which lets you streak around slicing everything in sight with a magic sword. the golden gun is basically a one shot kill for so many shots. and the new one is a magic bow and arrow, one of the perks to it is it does damage and anchors enemys in one spot. the Warlock has Voidwalker where you shoot a massive void ball at people that explodes and kills them. the Sunsinger is basically a revive you can be killed and resurrect yourself. the newest class is basically you turn into emperor palpatine and float around shooting lightning out of your hands which is pretty fun.
the really cool thing about the game is that different classed are really good at certain parts of the game, like you could actually solo the second raid as a hunter or titan fairly easily once you got the higher level gear and weapons, you could do this as a warlock as well but it was much harder In my opinion. the raid was just one example off the top of my head and in all actuality it was kind of a bad thing cause it broke the game basically and didn't force you to work together with other people. the new raid however has seemed to fix this problem and it requires a lot more teamwork. it's more immersive now if one person on your team isn't doing their job it's a wipe. now this will change slightly once people start getting geared up more and i'm sure it will be a little easier to carry a lower level character through a raid but it will still be tough.
All around i'm liking the new expansion a lot. the improvements from last year are huge and have fixed a lot of problems. some of the problems that they fixed are the things that you didn't even realize were problems until they changed them.