I don't recall Widdershins being that difficult.
Say, have you done the first or second or so arc by that Arachnoid exterminator guy? His name slips my mind, but he's dressed like a bug exterminator, hard to miss.
So anyway, he ALSO has an Arachnoid EB, just like Widdershins, but with the added bonus that said EB also runs away like a coward. If you cannot beat Widdershins, here's a friendly hint: If you meet the other Arachnoid EB, get a team with you, or chances are, you'll fail the mission and your failure will be forever immortalised in your souvenir... or until you use Ouroboros and 'fix' the time line, like I did when that stupid EB fled from me.
So, I'm playing my new Dommie and working through the CoV content (which I never really did with my only other villie because I rushed her to 50 to keep up with a friend.) I am striving for story arc completions in addition to badges, but I stumbled across this evil arc from Dr. Forester with an arachnoid EB named Widdershins. Normally I can use a few inspiration to power through an EB fight with Domination in effect. This critter, though, ouch! Now there is some insane regen. Is it like this intentionally?
I literally held the mission until I was even con basis with him and it still took quite a while to power through him.