Finally cleared all the missions.

The best success I had in ?-2 and ?-6 was with a squad of girls set up like this:
T1 Damage 48K Speed 720
Rest of the Teams Around 48K damage, Speed 550-600
Suicide Bombers. Nuke one or two nodes and make sure to get wiped on the boss fights.
It still is RNG based however this way IF you get good RNG at least you wont fail with one strong group clearing the map before all nodes are hit.
Setup for ?-2
T1 Alone at bottom, everyone else at the top mass RNG route.
Setup for ?-6
Two teams (T1 and Helper/T2) at middle, rest of the teams on top.
Took a while to properly gauge the necessary DMG/Speed ratio for the teams, but eventually this setup brought me the 3* Victory.