While players can look to see GM as an achievement, I've only seen one player fighting mobs all the way to GM, during the last three months, and it seems that after he reached GM, he stopped playing. This is probably an isolated case, but it does deserve mention.
If GM were removed, would there have to be any difference in the xp required to level, as you can only have 4 tiers worth of skills/spells?
Hmm..perhaps instead of the quest machine showing easy quests, medium quests, difficult quests, perhaps group them by combat intensiveness instead. As a new player two years back, I sort of catapulted into a few quests with heavy combat intensiveness, got my ass kicked, and vowed to GM. Then after I GMed, I found the 'easy' quests with no combat intensiveness....