Let's say I'm going for an enhancement that requires 17 Dex....I should be able to start with 15 Dex and eat a +2 Dex tome and qualify, correct?

If so, then the DDO Character Planner should consider that in its next update. Other than that, I'm loving the planner....except for not popping up enhancements I qualify for and it makes me go to the next level to select it.