I don't know if equipment cards specifically designed to be cursed are necessarily a good idea, but the idea of cursing equipment is definitely a good one. If casting equipment on useful slots and then cursing it is a problem, then the curse could be restricted to enemy equipment only. Of course, equipment swapping isn't terribly common, so I suppose you could also curse the mage to fix all of its equipment in place.
If you can cast your own equipment on the mage and then curse it, it might block a strategy of theirs, but they still get a free piece of equipment that their opponent had to pay for. Since it can't be mage exclusive equipment (I think), it may even be equipment they can use.
Also, with corrosion entering the meta, armor swapping may become much more prevalent, so cursing armor could be an excellent counter.