Corrupting Blood?

I have my first character nearing Dominus in Cruel and things have been a cake-walk so far, but for one Rare mob I encountered on the way to Piety. It was crazy!

The mob had the Corrupting Blood mod. Without even hitting me, by merely being on the same screen, I had stacks of corrupted blood piling up --- around 3-4 stacks per second. The first time I saw it, I hit 16 or so stacks and almost insta-died. I ended up kiting it from extreme range (so I could get outside the range of this effect the moment I had a few stacks) until I could kill it. Had the mob an Energy Shield or Life Regen, I would have had no chance, and it blocked access to Piety so I had to kill it.

I presume there has not been something as ridiculous as this seemed in the game this long. There must have been an easier way to handle this situation, but I was completely thrown. This nobody was more dangerous than Dominus/Normal :P How do I handle this situation when I inevitably encounter it again?

You get a stack everytime you hit the rare mob.

Staunching Flasks removes all the stacks.

Since the damage is physical degeneration Endurance Charges can help a bit and Immortal Call makes you immune to it entirely.

Flask with "Removes Bleeding".

Corrupting Blood inflicts a bleed stack every time you hit the mob with any skill. Basically the only way to deal with them is to have a staunching flask to cleanse the stacks. It also soundd like you might have a mob with high physical damage (which is what the bleed damage goes off) which is a little unlucky. But yes, get yourself a 3-use staunching life flask (or other flask if you're ES). Such a thing is very useful against other sources of bleeding too. Having some life leech also helps a LOT, as it lets you tank the bleed and get some damage in before having to use your flask, so you can actually kill it before you run out of flask charges. Finally, if you have the ability to set up a cast when damage taken - enduring cry - immortal call combo that will make you more or less immune to the bleed.

Side note: the reason you haven't seen one until now is that they require monster level 40 to spawn.

Oh, I got the stacks when I hit it! I thought only Reflect worked like that. This explains why the stacks seemed to be coming from nowhere. Thank you! I was using fast attacks to try and burn it down asap when I obviously should have taken a slower, one-big-hit and kite approach. I will have to take that particular mod into closer consideration in future: definitely the most dangerous one I have seen so far.

I have a Quicksilver Flash of Staunching, but only two charges. Still, two charges would have been enough that time if I realised.

For these specific mobs you can also use a Searing Bond totem or another gem that does damage over time like eg. Desecrate, because DoTs in PoE technically do not hit the target, they just affect them like an aura or curse would. Though this won't prevent you from getting bleeding stacks in the Dominus fight, so keep the flasks too.