Its fast... very fast at the start, slows down around 15 range, gets really slow at 18-19, and "holy shit are you crazy lvling" at 20+
also the 1000 mob kill achievement
also here's a solo aldgoat nanny at lv20 pug (22 physical)(red physical/class exp) to give you an idea of how brutal it is (takes 20,000 class exp and about 90,000 physical exp per level)
this takes awhile to kill still btw since my punches (heavy) only hit 30-40 and it has like 1000-1500hp) also may have not been possible without shock spikes buff.
Yellow con mobs hit me about 120-140... pretty much suicide, light orange hit like 180-220, pretty much going to die before taking it down 1/4th
I'm sure seeing that you can guess how long it will take to level!