Just move from the imps before they explode if you don't have damage to single target them (which you prolly should have with inflated ilvl + valor upgrades).
Tbh gear someones alt if they have a dk, the fight is very difficult and i cant picture doing it without a dk (or 2), just like doing xulhorac without mages, tough stuff.
Gear two alts, there are 0 fights register (on warcraflogs) without dks. The fight is quite difficult (and long), you won't be able to defeat it without (at least) a dk (it will take less time to gear 2 alt dks in 2-3 weeks and then try the fight that going without them).