Originally Posted by
Answerer
You're ignoring some important details here.
First, there's the fact that a lot of the utterances in Tome of Magic are really weak. Especially at higher levels, even though you can use your utterances doesn't mean much, because you don't really have any good utterances to use.
Second, and more important for this argument, the Truenamer takes a lot of optimization to hit those DCs. A low-optimization Truenamer (nothing more than max ranks, 16 starting Int, +6 Int item, +5 Int from levels) is not going to hit a lot of them. You can optimize the Truenamer into playability. But no other class, not even NPC classes, has that requirement. That's why the Truenamer cannot be a part of the Tier list. It simply cannot fit in what is supposed to be an optimization-agnostic list.