According to Warmane rules, your MS for that specific RDF run = whatever role you go in as, unless you gain explicit permission from all other four party members.
Assuming the above interpretation of your words is correct, you would have been, from Warmane's point of view, 'a healer rolling Need on a DPS item', which does, unfortunately, fall into Ninja-looting category. As to whether you'd actually get that ban, I cannot say. They don't really give out these bans that lightly, but if the mage has sufficient proof, then yeah.