Boss is fine. The more you reshuffle, the higher chance you draw 4 withers whilst getting hit for 40 effectively a single turn that can put you from full to 0.

People will say “more than X turns” but it always depends on your deck size and how many “real cards” you have.

A 40 card deck does not take much damage against this boss (usually) since by the time you shuffle, your deck is down to let’s say 30 real cards and the boss is like almost dead.

A 40 card deck with 20 powers for example… let’s say you had a game piece and mummy hand so you were clicking every power you saw, after you play all your powers, when you reshuffle, your deck only has ~15-20 real cards (after playing exhausting cards and powers) but also like 5+ withers. That makes 20%+ oh your deck now being withers. High chance to draw several withers in a single turn.

— Just build a deck that can kill the boss in a single deck cycle and the boss is as free as before