Diehard and Greater Spell Focus.
Diehard is, as I said in the previous round, a sucker's feat. Someone argued that it is cool as a roleplayer's feat, but I don't really see what Diehard does for roleplayers that Improved Toughness and, well, roleplaying can't do.
Greater Spell Focus is just too weak. Spell Focus was weakened (and rightly so, IMO), but weakening Greater Spell Focus made the combo too weak. +4 for the two feats was too good, but +2 for the two feats isn't good enough. Since the design philosophy behind feats is that later feats in a chain should be more powerful, Greater Spell Focus is the culprit. Get it outta here.