Terramorphous drops?

Anybody having problems with terra drops? I’ve farmed him for about 5 hours today and 5 hours yesterday day and it only takes me about 2 to 3 minutes to kill him and I’m trying to get the boatmurderer head for the zerker and all he’s dropping is greens blues and siren slayer of terra mods. No purples whatsoever or any other class mod. Anybody have this problem?