If tier 1 cannot handle every situation, then it is tier 2. The definition of tier 1 is that it is useful in every situation.
Okay, so for, say, the Truenamer. If you fix the broken aspect of it (skill used as a DC) does that mean that the base Truenamer is not broken? No way. So you say this is a definition issue? So going by the definition of redcuing power, you are making the classes less powerful by removing the overly powerful aspects of it*.....how is that NOT making the classes less powerful? I mean, really? Okay, this is the deal: The casters have overpowered abilities*. Removing these abilities will make them less powerful, by definition (they are of positive value, and the casters no longer have them, therefore the end power is less than the start power). However, your argument is that because they are so overpowered, they are automatically removed from the game?
*These being......okay, why don't you list what are overpowered? I know infinite loops and no-save ability damage (Shivering Touch) are on the list, but what else?)