Struggling with GW at some stage is normal. My best advice is to just work towards Wiggs, they really are the stars of GW with their strong self-healing. Until then try to play all useful toons in the early nodes to activate their TM if you need them later on. Mixing up teams is important, so the question "which toon to switch" is dubious to me. Ewok Elder is useful too as he can revive fallen toons, but must be starred, levelled and geared to have enough health / protection as other teams like to shoot him first (ok, in this way he protects the other toons as well, but it's better to have him alive).