I did it with Corso.
Interrupt his 1st buff as much as possible, (did it 3 times: flash grenade, kick and range interrupt) Poured as much damage in him before Corso went down. When he got close, Hunker Down. Got a kick in before it ended. Medpack and Defensive CD's and Diversion when I got low.
Just a note. It took me a handful of tries because Corso would die around 10% percent and around there his harpoon would make him LoS. (More my fault than anything else) Also that last 20% is pure burn phase. Because he starts hitting like a truck once he uses his spice