I don't understand - I think the 463 scaling is a pretty important concept to PGs. At end-of-xpac gear levels, you can essentially stack something to make your job infinitely easier (whether it's DPS, heal, or tank), so encounters get more mechanically difficult to make up for the ease at which you play your class. PGs are the opposite, they are mechanically easy (they just require a wide breath of your abilities, not just your 1-6) but are a strain on your actual role - hence the "proving."
Any HC raider whose been doing heroics for more than an expansion knows that there's nothing more difficult (and very little more satisfying) than killing hard heroic bosses in early expansion blues. What do you think world first raiders relish? Killing bosses in low ilevels. When I eventually kill H-Garrosh, my ilvl will probably be 10 or so higher than these WF raiders, and people after me will have even higher gear. In a gear progression game, gear nerfs the difficulty of things, and gear equalization (like in CMs and PGs) tests skill better than scaling mobs up to your ilevel. Our disc priest, who is, granted, the best priest I've ever played with, constantly complains about how boring healing gets as he gets more gear, because he's not worried about spamming big nukes.
As another anecdote, I was pushed into heroic raiding by early Cataclysm heroics. Our resto shaman in our casual guild was trying to heal that Tol'vir heroic and failing miserably, and insisting it couldn't be done. I had leveled my spriest first, so as a challenge, I thought I'd level my shaman to see if healing was really as difficult as he said. When I got to 90, and was healing those unnerfed heroics, I was really working, and struggling, to conserve mana, weave healing waves, lower my overhealing, increase my efficiency, until I was the healer everyone wanted to queue with. This pushed me into looking for like-minded people in a guild, that got me into heroic raiding because my old guild couldn't kill Magmaw, and I joined a guild which went 12/13H (we said a big fuck you to H-Ascendant Council 10 man), and then rocked every tier since. I've since switched to hunter, but the attitude was bred in those early heroics, where the gear simply required you to be more skillful because you couldn't make it up with gear/
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