I had this issue too...had Luke at lvl 70 and Han at lvl 72, both G8 6*. Did a quick boost for booth to level 74 and pushed their skill levels as far as that level could give them, each with average 3* mods, and then swapped them around as leaders (luke was first), and it suddenly made all the difference.
My Han taunted immediately, and each couple of hits gave Luke tm to fire back in response...with Luke at that level he suddenly started hurting a lot more, and took down both Stormtroopers before Han's taunt wore off (I admit I had some lucky RNG there too).
Ignore the officer and later, the desert trooper...they may fire a lot faster but they do much less damage, have too much health, and their attacks on Han help boost Luke's TM even more. I did lose Han at that end but by that time Luke was on a roll against the last 2 troopers...the desert trooper never stood a chance...