what are the 2 - 3 best pets to use to kill him ASAP?
Not sure if Phantom/Satyr works better for disco either, but I & a few others have always used Centaurs. Level 15 Skeletrex isn't much of an upgrade over a level 10 Centaur, so there's no real need to use it, IMO. This method requires no healing, just you watching his bar go down.
Another tactic I know of (that I've never actually used) involves a Promethoid, Naba, and Darkmane. Naba casts/DP's/melees, Promethoid heals, Darkmane chains AI. It likely requires that you need to heal the pets as well.
What about hit lower defence?
If it also works, it could be interesting to have a dexxer there with two bards running peace and provo masteries, and a 30% physical eater suit whacking at Andross to make it easier for the creatures to hit him.
HLD doesn't work on monsters. If it did, my Sampire would have a MUCH easier time hitting Neira. And, well, every other monster in the game.