I unlocked using these:
(HP = health + prot)
Juhani: G8, 195speed, 41k HP
HK: G9, 202speed, 36k HP
Ordo: G8, 189speed, 32k HP
Carth:G9, 203speed, 43k HP
Bastilla: G10, 232speed, 47k HP
Mod HK with damage, Bastilla with speed and survivability for everyone else.
T5 is the only hardest phase as I can see. - - Avoid attacking enemy with Fear.
- Only use Bastilla's Wild Lightning on enemy with Shock debuffs (from DR's Force Storm).
- Save your specials on phase 3 for phase 4 if you can
For T6, just focus on Bastilla, don't bother with the droids since they'll just revive.
As for the last tier, use the same strategy as T5. Utilize Fear correctly and you'll be fine.