well, if the fight is intensive, i would use LA at around ~70% mp first time, maybe 60% being lowest, it coupled with AoE buff or anything else, then use CU to extend refresh with 5 more seconds and extend buff on people for 5 more seconds.. after that for 2 minutes of it's cooldown not much you can do than if you really need mp, to hope for ewer.

balance/arrow for spread, very rarely ewer. for ex roulette dungeons sometimes bole, whatever best comes up while dealing with trash and waiting for boss.

not much to say about DPS. Combust 2 + combust 1, and then just spam Malefic 2.
At lvl 50 you can use aero1(200p) since it's potency is higher than Malefic1(150). At 60 i still have aero but use it mostly only when there is some movement.
other than that, for quick burst dps, it's just spamming malefic2 and that's it(if need to kill adds quickly that dont have that much hp to take advantage of DoT's).