Actually I am 100% confident you can do it with your current Ig88. Mod him for complete survival and speed though. If you can go all defense% type, crit avoidance arrow, then all secondaries speed defense health and prof, still manage to get him to 180 speed with a cd triangle and protection cross/circle and 45% CC, he won't die often and you'll in 15 attempts. Don't worry about the whole waiting for Chewie to not be stealthed thing. With G12 zBOss your tank is beefy enough to fight through. Just make sure Bossk is around 220-240 speed and his tenacity is around 60-90%
I did it without Dengar and I used Ig88 Bossk Boba Greedo and Cad. Bossk and 88 were my g12. Rest 11.
All that said. Dengar is incredibly useful and you have him well enough to use your 88 for a off droid GA team and other 5 BH for off offense B team. And Dengar will be a better BH ally in the end.
Get Dengar