If you have a level 85 team of Boba lead, Dengar, Cad Bane, Greedo and IG-88 you can definitely get T6 with modding correctly. Let’s take a look.
Do all your BHs have their payouts maxed? Have you spent your omegas on their abilities? Boba should be Crit Dmg and Crit Chance mods and the others with all high potency mods and sets. Are your mods 5 star and level 15? Boba’s leader grants bonus health to all BHs based on potency of the entire team. Boba needs Crit to execute.
Are the Gear Scores good with at least Boba being the highest possible at GS 10 minimum? The others can be GS 8 or 9.
Do you understand the mechanics? On opening Dengar must be critically hit to trigger his stealth which causes R2 to waste turns trying to stealth the Rebels. This is triggered by either Chewie slamming the team causing a Crit on Dengar or someone shooting him. Boba can not have ability block on him, so ROLOs opening salvo has to be monitored for what damage it inflicts. If either R2 is able to stealth the team or Boba is ability blocked, restart.
Kill Chewie with execute, kill Han and finish the payout. Kill Rolo Lando and R2. In that order. Dengar and Boba May be the only 2 left standing but congrats you own Chewie. It’s pretty much the same for phase 6 and 7 only harder.