If they made 31 easier to get to people would just bitch that 32 is too hard or something. I think the xp required from 1-30 and then 31+ is spot on, the only problem is hierlooms.
There are people in this game that are fucking incredibly awesome to the point where it is almost hard to believe it is real. New dudes see people tearing mad shit up with 15 kills a round or something insane and want to be that guy. No one wants to admit they suck at the game so they just figure once they get to 30 they can tear shit up.
"Uh oh now I'm level 30 and I still get my shit pushed in. Well, I bet once I get some heirlooms I'll fucking tear it up."
"Hmm this heirloomed weapon doesn't seem that great, well maybe I'll loom it again because then it gets some speed bonuses and that is where it's at."
"Well shit, that didn't help, I still feel like I'm swinging like a retarded monkey. I bet I have an idiot build, fuck I'll fix that next time, get some more AGI or WPF and it will be all good."
"HMMMMMM I've got a 2x loomed weapon and 24 agi what the fuck is the deal here. Maybe I'm just bad at this game. Perhaps I should have spectated awesome players and really try to see what they do instead of alt-tabing out when I die to look at all the awesome gear I'm gonna buy."
I never played M&B online before and that was my exact mental processes when playing through. It took me about 5 gens to realize, oh shit I'm bad. Some of this was on the old gen system so it was easier. But as long as there are benefits for leveling up more people are going to try and grind them eventually. And even though a few heirlooms won't make you a monster, 9+ of them will really give you an edge. I don't know what to do about it, except maybe give a flat limit on heirlooms per character, perhaps 1 per category of item or something.
The 31+ bonus was designed as something for hardcore grinders, not really for everyone and especially not for the person who just plays 1 hour a day. The problem is that as long as it exists people are gonna want it, because other people DO have it.