Any chance of using two Skull Lords instead of one elite? Our last epic game the PCs had an encounter with two pseudo-skull lords, a horde of minions, and a trap. They were Skull Lords advanced to 22nd level in their stats, but I changed the flavor to Yuan-ti to match the adventure. Instead of Fear it was whispered commands and they were snakey instead of undead.
The two "Yuan-ti Malison Venom of Life" coupled with our minion house rules and a poisonous trap was pretty tense. It wouldn't have been near as challenging if there had only been one of them, because double hit points doesn't give double actions, and leaves the monster more vulnerable to secondary effects like dazed, stunned, and foreced movement. The +2 to saves helps, but having two bodies means its harder to shut the powerhouse down completely, and much more likely that if you manage it, it won't last long.