While doing this, I did a fair bit of testing in a way that just put the numbers on my screen, and also combed over the improvement functions very carefully. Couple of general truths:

1) Ability improvement is somewhat easier at higher levels.
2) The incentives dealing with being grouped and fighting bad-ass hell beasties are positive.

As for those spells not improving: Could have been bad luck. Could have been a fight where one party could not harm the other directly. Etc. If you want to email me with more specific details (spells in question, etc.) I can comb for whatever.

valguarnera@carrionfields.com