Idk what I’m doing wrong

Use just Dedra, Kleya and Vel team.  You have to time undermine so you do the most damage before the boss cleanses itself.  Dedra is used by herself until major P comes out tomorrow.  You’re fighting a spreadsheet.  It’s RNG with a 40-85% completion on the boss at era level 55 until the next toon with leadership and Cassian land. Then you’ll do it all over at tier 6 and get auto banned if you make it to tier 7 at era level 65.  

Just auto and leave it there because its a paywall after. For future ones you dont need to pick all the toons as the level will fill.

Poor poor game concept. Its a not you its me thing.