I haven't but you might try this:
use a spell sequencer on the demon to cast
ierce magic, lower resistance, lower resistanc.
Summon a couple of fire elementals to keep the maraliths busy (also they are immune to fire damage).
use another spell sequencer type for several firballs directed on the demon.
prob. another pierce magic and more assualt magic on the demon.
use a monster summoning wand (it is fast) to play w/ the maraliths and a breach on each maralith (have more lower resistance spells ready).