Just got passed the bonus tier by the skin of my teeth.
HK, IG-88, B2, IG-100 and IG-86. (All gear 10)
Take out the scouts as priority in all stages except for the final stage 8. Stage 4 also requires slightly different tactics and a balance between attacking the Elders equally as they'll revive at full health and Area attacking scouts. Ignore Teebo.
Use your AoE attacks wisely, I save mine for the stages with scouts, once they're out of the way use the shield special for health as you basic attack the tank Ewoks.
At the final stage focus on Elder as priority, then scouts, then Chirpa. It's a bonus if you can take Elder out early with 86 ally calling attack and 88, as you won't have to face a second auto revive of Ewok Scouts.