I was wondering about this when I watched that WW Barb GR61 solo video. It was impressive, given that he was actually able to kill the RG--even if it was one of the easier ones, he still didn't even try to dodge her slam attack that I thought would one-shot anyone at GR61--but I felt like the progress bar moved way too fast compared to the amount of trash he actually killed. Now that you mention that, it does kind of look like picking up grapes gives much more progress to the bar than on live.
Well the PTR has a 300% xp bonus, which I think is multiplicative, kinda like how the 2000% legendary bonus seems multiplicative. It could be additive but I leveled my Wizard on PTR before I started farming on it, and I went 64-70 in like 20mins with only the leoric ring on master difficulty, which seems way way faster than on live, I was getting like a level per bounty when I think at these levels it's usually slower(but then again I don't remember for sure).
So I wouldn't necessarily expect a 61 clear at the same speed, especially if they end up nerfing shit anyway. Plus it'll take a while to find the same items on a live server.
It's still impressive though and no other class comes close I think, the second highest is like 54 with Wizard iirc. Which is interesting on its own, since Wizards were fairly garbage pre 2.2 but that Tal Rasha stuff is brutal damage(though it was nerfed so the clear might have been prenerf not sure).
And yeah on loot I'm not a big fan of live drop rates still. It's obviously a ton better than a long time ago, but then again back in 1.0, rares were actually useful. Rares are literally shit nowadays, they're worth even less than blues and whites cause those are actually rare that the crafting materials from salvaging them is worth it, while rares you just stop looting after a while cause there's no fucking point. And then you have a bunch of worthless legendaries(no special affix or terrible affixes, although they've been working on fixing some of them this patch). And only then can you get maybe the good stuff, but it's just for the bonus at this point, since the odds of finding it with an Ancient tag and well rolled is stupidly low. There's so much RNG on top of RNG, I don't get why the initial acquisition RNG has to be so shit. It's not like if you found 1piece of your set every 10mins you wouldn't need like 300hours to actually get all ancients with good rolls and the right stats(especially shitty slots like amulet/gloves/rings that need to roll very specific affixes or be shit).
It's especially bad since they put all the power on sets. Builds are sets and sets are builds, you can't make a build that isn't based on a specific set because sets are so strong they entirely define your class viable builds, at least past T6. And sets obviously mean you need to find several "legendaries" in specific slots to actually complete your set. Some classes are barely even viable before they finish the full 6pc(like crusaders).
Kadala is supposed to help since you can gamble specific slots but the loot tables are so large for a given slot, especially when you have a class specific item for that slot that it's almost fucking useless.
And then they make some legendaries more rare, for no fucking reason at all.
I still think their system is fucked, considering the lack of trading. Lack of trading is more than fine, but shit should be raining down, it's not like people will get perfect gear unless insane RNG or playing 3months or whatever, which is the length of a season. A lot of those people pushing high GR that play 10+ hours a day aren't even close to max gear. They have all the pieces, but the rolls aren't perfect and not everything is ancient and shit like that.