I think there should be a daily limit on ZP's, maybe that'd stop people dragging other people through tiers of content in a week..
Tank
The best way to do that and incorporate ZP drops in my opinion would be to have 2 different ZP items. One would be the one that is currently only drops in game in the Halloween event whenever that is live, (if that is the correct information). The 2nd would be one that would drop wherever, would be lore, unlimited casts but a really long cool down. Maybe have different tiers of it to reduce the cool down. Or could even be a quest item that could be upgraded like several of the other items we have. Just some thoughts.