I'm currently level 23 almost 24 now, Realm Rank 19 breaking in game 2days played. The pace of leveling has significantly decreased, especially quest experience. Albeit, it's been a few weeks out since release, but I hope Mythic scales quest experience post Tier 2 (levels 22+) like they did in the earlier Tiers. My guild leader, who is level 32, calculated that from all the quests in a town he could do, it wouldn't even yield him a percent of overall exp. Quest experience seems to cap at 3200exp.
Some other concerns I foresee lie with Scenarios and Public Quests, regarding population. What happens to newbies once everyone makes it up to Tier Four?
My class, White Lion, is one of the least underplayed / underpowered but I'm still having a great time with him. I think some love will eventually come my way but I hope they fix Squig Herders and Magus' pronto. They're even worse off than me.
Overall, I will subscribe for at least another month. It's a fun game, especially with guild groups.