... the problem was that for some unknown reason, the boss's damage shot through the roof...
From a strat guide found on the internet.
Putrid Shacklaw is a lvl 50 champion with 112,376 hp. This boss has two abilities:
- Self buff Overwhelming (Hits from these massive beasts slow targets significantly)
- Ground Marked Yellow Circles (moderate ammount of damage )
the one in red is certainly what you experiment.