1) The top #1 meta that everyone blindly copies, which is support barb, support monk, generator monk for single target, Firebats Arachyr WD for most damage during the rift.
2) The speed run meta which everyone should run. On SC, people seem to be too stupid to understand that and switch, because no one ever wants to try anything that's not rank 1. On HC, people understand that for speed farming is monk+barb+2x wizard. It's even #1 on HC right now: https://www.diablorank.com/grift/season9/hardcore/4players/class_126/region_30/page_1 so I guess it's established as HC 4p meta already.
Wudijo also made a nice video about DH in groups (link), which is for SC but it might still be a viable option (though not the best). Last but not least, a class/build that is really underestimated at the moment is the Hammerdin crusader. You can see in 2 player that it's slowly picking up and showing its potential.
Basically, you and your friends can pick *any* class. Also keep in mind that switching classes takes close to no time in Diablo 3. So here's the breakdown:
Barb: Is mandatory support in 3 player and 4 player speed GRs after 80+
Crusader: Is an option for speed farming or in lower groups, probably a good DPS choice for the barb which will feel useless in GR50-GR75 gem upgrade rifts
DH: Is the #1 for Torment speed farming and everything up to GR50, and with the new Grenades build an option for lower speed GRs as well.
Monk: Mandatory support monk in any group (2p, 3p, 4p) after GR80+ (maybe even earlier on HC). A second, generator single target DPS for super high pushing at the moment. But you can probably get away with not playing it until the last week of the season.
WD: Firebats Arachyr WD is currently the #1 area damage DPS class in high GR pushing, but for speed wizard is probably a bit better (more mobility).
Wizard: Has several good speed farming builds (Archon with Firebird, Archon with Tal Vyr Manald Heal, Archon LoN for T13 and low gem ups) and even a support build.
Choose wisely! (Hint: "wisely" here means "the class you like".)
There are two metas:
1) The top #1 meta that everyone blindly copies, which is support barb, support monk, generator monk for single target, Firebats Arachyr WD for most damage during the rift.
2) The speed run meta which everyone should run. On SC, people seem to be too stupid to understand that and switch, because no one ever wants to try anything that's not rank 1. On HC, people understand that for speed farming is monk+barb+2x wizard. It's even #1 on HC right now: https://www.diablorank.com/grift/season9/hardcore/4players/class_126/region_30/page_1 so I guess it's established as HC 4p meta already.
Wudijo also made a nice video about DH in groups (link), which is for SC but it might still be a viable option (though not the best). Last but not least, a class/build that is really underestimated at the moment is the Hammerdin crusader. You can see in 2 player that it's slowly picking up and showing its potential.
Basically, you and your friends can pick *any* class. Also keep in mind that switching classes takes close to no time in Diablo 3. So here's the breakdown:
Choose wisely! (Hint: "wisely" here means "the class you like".)