Should all experience be account wide?

This isn’t one of those times I know what I think the answer is, I’m seriously just posing the question because it occurred to me yesterday while playing Heroes of the Storm that I was kind of hurting myself by switching characters. Sure, you have player XP and character XP in that game, but I’m in no danger of unlocking any of the master skins any time soon.  This is because I played Varian, Muradin, Malfurion and ETC over the course of fifteen matches, instead of just sticking with one of them.

The same thing happens in World of Warcraft. I focus most of my attention on my first Warrior to 110 because she’s the most advanced, and leveling other character sets me back.

It made me think about Paragon levels in Diablo 3, which will give you a boost in power to your less advanced alts. But even that isn’t actually account wide experience — you still have to level your 19 Witch Doctor after you get your Crusader to 70 and start getting Paragon. Would a system like that work in WoW or other Blizzard games? Or am I just too old and bitter for this, the key mechanic in so many games I’ve lost count at this point?