SMN on Turn 5 Phase 2 and Phase 3
SMN is very difficult make Turn 5 work due to Phase 2 and 3 needing very heavy burst. But there are ways to make it much easier. Memorize when conflag will pop. Throw your DOTs up just before that and then AOE your DOTs with Bane. This is IMO actually one of the best burst mechanics in game but only works when you know when a pop will occur. If you can manage your MP very very well in Phase 1 you can save extra stacks of Aetherflow and have a another Aetherflow CD ready and then you can Bane AND Fester conflags. Also your pet does count toward group stacking for conflag. The more people that are hit by the fireball attack the shorter the duration of conflag by i think 3-5 secs per target hit. So you have to position your pet accordingly to your strategy for handling that mechanic.
Snakes are a little more difficult as you need to reapply your DOTs after the adds die for the full benefit. And TBH the adds need to die before the total length of SMN DOTs including the time it takes to cast them and then to use Bane. So SMN does really get screwed on Phase 3 due to heavy lack of AOE burst. With 2.1 this should be easier with Blizzard II, as long as you can manage to move out of the way before the snakes die so you don't get debuffed as well.
Personally I spec PIE and have astral jewelry with +9 VIT and +6 PIE on each piece just be able to have a higher MP pool and greater MP regen for things like this because being able to sustain full DPS (to prevent enrage) while saving as many Aetherflows as possible for the bursting gimmicks is essential.