[phiwum]

Seems to me that all you've said is roughly this:
(1) New spells are a constant cost.
(2) Increasing mana is a constant cost
(3) New talents are a constant cost so long as you have the prerequisites.
(4) New attributes are exponential in the long run.

Add to that the following:

(5) Some talents require prerequisites.

And then we may conclude that wizards who don't give a damn about attributes sure do improve faster than warriors who focus on really difficult talents like UC. Which is a little less sweeping than "Wizards progress linearly while warriors progress logarithmically."

It's a really odd bit of analysis. Especially given that, at least in my experience, most characters end up somewhere around 36 to 38 attribute points anyway.