The latest version of the game turns the Devil's Pit into a settlement, so look for the two respawning pirates in Skellige, as shown in the video.
For me the following combo worked:
- Devil's Puffball for poison
- Igni with Pyromaniac for burning
- Broadhead bolt for bleeding
Just rest and they will respawn, the cloud from the grenade should still be there, so if you see the pirates already losing health you can just skip to Igni. Turn the difficulty up if they die too fast.
For the video all credits goes to Ben-Gun