And packing six purifies doesn't shut down any poison deck? Everything has a counter, even Dark Matter is beaten by mono aether. Does that make mono aether OP? Sure, this card could make Scorpio much easier, and maybe Morte a bit, but that's 2 out of 24 gods. Against the rest, there are much better weapon choices.
This weapon isn't OP at all, even flying and adrenalined, when you place it next to a druidic staff. It would likely only add two counters in the four attacks, as that's what poison-appliers do. Since it only adds one purify per attack, not to mention that the attack has to be successful from a 2 damage weapon, the cumulativity can hardly compare with the staff's 20 healing per turn.
If it's really a problem, just cap purify healing somewhere. Maybe even reset the counter when poison is applied, since that's what purify does to poison. So if you have +12 per turn from purify, the opponent plays a deadly poison, you go to -3 per turn from the poison.