I’ve fought Nel twice (once around level 30 in NVHM and another time around level 50 in TVHM). Both times he dropped a Skullmasher. That’s 2 for 2.
What are other people’s experiences here?
I know I probably just got lucky. Though I suspect he also has a higher drop rate for his legendary. Probably because it’s kind of hard to trigger him, let alone know to explore around.
The first time though, the skullmasher was sitting practically in the lava of the little canyon. Our 3 man team spent about 10 minutes trying to get it. Finally I managed to squeeze myself against the canyon wall + of course slowing my descent with my Oz kit, just enough to grab it before dying.