Fastest T6 farming is Condemn Crusader by far. They do retarded damage, they have amazing AoE, perma inmunity to CC, go thru mobs, etc. and they can do GR very good. TR monks are second in place and not Fire cause AoE is horrible. Lightning TR is way better than Fire, but requires better gear to keep up with spirit and still do decent damage. Multishot DH comes third in place, does more damage than the previous options but u have to stop to do the damage while the previous options u only stop to loot.

TR monks only need Sunwuko's and that's 3 pieces + RoRG. DHs need 5 piece Marauder + RoRG (Rucksack is not really mandatory for T6). Condemn Crusaders are the harder to gear cause u need full Akkhan set + Blade of Prophecy + Frydehr's Wrath and focus on high CDR to have perma Akarat's Champion.

My advice. Go with DHs. May take a little while to gear and are not the most efficient compared to the other 2 options, but they are still very fast. Also gearing them is not as hard and slow as other classes. Ranged chars are far easier to gear than melee. Once u get at least 1 DH with M6, u will go several difficulties up instantly if not T6 already. They do so high damage that just 1 can carry the whole party. And ranged rarely suffers from dsync issues, at least not as often as melee. U can always use them to get shards and then switch to gamble with other chars.