Just started to play again, please lmk which class is more fun/best etc for PvE ^^

And also which spec

Those stated classes are my lvl 100's atm

I could by the way also level another class.

I have a lvl 73 hunter and pala, 53 mage, and 60 death knight

Could also level a warrior i guess.

Arcane Mages crush pretty much every fight provided you learn how to use Rune of Power and manage your burn/conserve phases. Warlocks of all specs (spec depending on the fight) win on certain fights in HFC, pretty much uncontested. Unless you're playing to be at the top of the world in terms of numbers, just play whatever you want/what you're good at. Hunters are literally easiest to manage - smaller loss of DPS while on the move, so learning fights without absolutely tanking DPS is easy.

boomkin is really strong right now, also seems like a lot of guilds are looking for rogues and ww monks that arent braindead