This.

If you're looking for T10 opinions, you'll need to wait. PTR is not done and usually OP classes receive last minute nerfs before going live.

As for your question of what to run when you return. Wait for PTR to complete, give it 1-2 days, and google search "best build for [insert class here]" and just run that.

The ''fastest'' would probably be the Barbarian again, with the new cube, Furnace/hexing pants/(Coe/Obsidian/RoRG), it will be pretty quick. but sincerely, knowing that a 45 GR is approximatly a 40 GR now, T10 is pretty much a 40GR actually. (They nerfed GR a lot). So yeah. Maybe Monks will be good too, with the new ''setup'' --> https://www.youtube.com/watch?v=RMIEelAc7ss

but the funniest ? it's all up to you. Farming over and over again with a Barb can be really annoying and boring. Try to just go ahead with the class you like.