I guess it just depends idk. I was messing around on PTR with nothing but a level 25 powerful and got to GR 75 with wiz. Last PTR(before any nerfs) I did paragon 230ish invoker sader(though I had free set) and cleared 77 with lvl like 28 trapped and 30 thorns.
On live in S5 I did GR 77 as invoker in 2 tries at paragon 450 after ~20 hours into season. Now that that set is even more buff it will be like GR 82 that soon into season. Esp if you get a hack/provoke shield with the new setup.
Just depends how you play. I used no ancients and nothing op. Basically just crap non ancient items that you could get around that time if you had avg luck.
Sure others might have to be higher idk. Guess it depends how hard and perfect you play.