Hmm, really trying to find how and where this situation with tank doing DPS becomes relevant. I suppose it's like Twintania (pre-2.2) where you have 1 tank that is not taking actual hits, and need to burst DPS something (4 stack conflag in the Twin example). Also, has to be a situation where a tank needs to switch from taking hits to dishing dmg: If it was pure DPS the whole time, then you would just bring a DPS class.

Would be great if SE designed more fights that actually need this. But at this point I almost never see it happening.