For 35 points, you get +1W, +1 Ld, +1 DD and many more options. He can be the army general and supplier of DD at the same time. That's why he's the no-brainer option over a different General and a Warrior Priest. Neither the Ancient Heirloom special rule nor the better fighting stats of the TGM are good enough to compensate adequately IMO and any combination that gives you Ld 9 and 2 DD is going to cost way more.