The tank stats stem from an armored supplement I started writing awhile back. That and the corresponding tank stats haven't been updated in ages. Thanks for pointing out that the numbers probably need revision.

To your question, I see three basic options. 1. npc v npc is the GM's purview, so the GM can decide to escalate or de-escalate tension to push the story along. No dice needed. 2. In you example, a player could roll for the NPCs they are fighting alongside. See the move NPC Action. 3. If it seems like you're making an engagement move, do that instead.