Generally speaking, I have a roster to perform up to Master level for each week. Week 1: I managed to do Master 100%, with a couple revives for Ultron. CapIW at 4/40 was my main champ for the fight.Week 2: I managed to go through only the right side of the Master mode with ease, no potions, no revives. However, for the left side (with Vision & Sentinel) I have no real counters and got badly wrecked. My best performing champ there was Psylocke, who power-controled Vision to a point, but only at 3/30 she cannot turn the tables. On to the next one...
For Sinister, try spamming the Parry-Heavies on him to get Toxins faster, without as many loose Bleeds.