Driller tactics is needed

[Shadowcran]

4 back units:
Paladins
Inquisitors
Evil Beholders
Beholders

1 Tank:
Royal Griffins

Spells:
Phantom
Stone Skin

Have Resurrection up to 3

The Paladins are usually there to heal the back units. I group them together. For driller they need to be spaced accordingly so you can constantly move up one space every turn.

I simply send the Royal Griffins forward with their Angelic Guards. Cast Phantom on the Royal Griffins, and use Angelic Guards for those first thing(even when phantom leaves, the Guards remain). If enough mana, cast Phantom again. Keep the other units away from melee range. Don't worry about how many R Griffins you lose in main stack, with Resurrection 3 you'll get them all back, but you can stone skin them if you like.

As you can tell, you can replace the Beholders with any other ranged unit.

[the benevolent adversary]

seriously why take so much chain gun damage! bring only 4 units.
I use these 4:
red-dragon
rune mage
arch-mage
paladins
set the paladin on slot that puts him one space up. cast stone-skin and haste (mass if you have it helps) on the paladin.
next turn cast stone-skin on the dragons. use high damage spells when ever you don't have to renew the stone-skin or heal.
second-wind the arch-mages (if you trance first instead of shield you will get 3 uses of the trance). don't forget to move your arch-mage up each time (if you do not have mass haste).
anymore I do driller at around level 41 after I have done elenhal battle; I also do it as the last of the 5 battles from my first ancient knowledge (dwarf king, champion of teana, marquis and demonia being the other 4).
when you are this high a level you might not have to cast arch-mages shield or healing and might not see any droids spawn (as a warrior driller might not even have time to break the roof at all).
different pauses can change what drillers response is ,I restart for instance if he does damage to the rune mages.