Skill gains in all professions slow down as you gain in rank.
After level 20 it is painfully slow. At level 30 you feel stuck in the mud.
I can only imagine what it like at lvl 40 and above, since I don't think I will get there in this lifetime.
MA did this to prevent total uber-skill-runaway. The ubers are still uber anyway.
So the rest of us have SIB stuff to compensate.
Also, I guess its the only way that
MA could continue to claim that this is a game in which you can always get better, with no caps on levels, like some other games.