The moment the event description says g11+, you can't really complain that it takes hours to get the RNG to beat it with G9 toons in your team.
It's another problem that the event makes even a full G12 squad heavily RNG dependent, but once you have the required gear level, 1-2 zetas of the right kind (Bossk lead especially) and some decent mods you don't need to attempt it for hours any longer.
Altough, as you said, it should be possible to beat the event with your team. You need 2 crit chance and 4 crit damage/offense mods on Boba, with as much speed as possible. Potency sets on all the other hunters, all their omegas except for leader ability (you need only for Boba obviously). Potency cross on all your BH. Don't use IG's AOE, ever. It feeds TM to the other team.
Your kill order should be fine.
What worked for me for T5-T6 last time (I was heavily undergeared, this time I had full G12 for T7) is to load Lando up with some debuffs, while still trying to take down Chewy first. This way you have a saving belt for Boba if he dies too soon as you can execute Lando and get BH's resolve back on him immediately.
