Let me just give you a hint that pub groups are very very bad in general. It takes a miracle to be randomly matched in a group that is functional and that everyone is capable of contributing. It is thus better to find a group via a community or a chat channel.
The only pub groups that are functional are T16 rift runs and bounties since the bar is low enough that it doesn’t matter what class/build you use too much. For GRs however, a good group requires at least 1 support character and good team synergy.
The GoD set is strong but not overpowered when you consider Necromancers, Witch Doctors, and Crusaders in higher GRs. The DH build is fast though for speed runs (but even then conventional LoD mages Necros can outperform it).
There are indeed balance issues which might be somewhat addressed in the next patch but I don’t think DH need a nerf aside from a change to missile dampening monsters.
Paragon levels don’t matter so much until massive amounts are obtained. If you have around 2000 paragon, going to 3000 paragon will maybe grant ~25% more damage which is about 1.5 GRs worth. The real benefit from paragon is that in gaining those levels, you likely found far better gear to bump your character up a lot.