[TippetsTX]

At the risk of straying off onto another tangent, the issue (as well as the solution) is more tied to how TFT handles task/action resolution IMO. The default 3-die roll mechanic is fine until stats raise to the point where the chance of success is a forgone conclusion. The fix, however, is already built into the rules. Whether you stick with the 'tiers' for talent/spell acquisition based on IQ or go with something like my approach, advanced talents and spells should become harder to perform in order to stay in line with a character's rising attribute scores.

For example, what if more complex spells (say IQ 13+) required a 4/DX roll and the truly epic spells (IQ 18+) could only be cast by succeeding on a 5/DX roll? When this logic is applied consistently across all PC stats, they are much less likely to outpace the challenges that more experienced characters should be facing (and the talents/spells that they are using to face them) which in turn helps to foster much more satisfying gameplay in long-running campaigns.