Honestly (and this is just a theory) based off of Dessicus's dialogue, he doesn't really seem like a "death worshiper" like his followers. He seems like he's just an arrogant a-hole who wants to prove he's the best. Maybe the whole "death worshiping" thing is just some sort of trick to recruit people who believe that stuff into joining the GenoHaradan.
Kinda like how Hulas tricks the player in KOTOR 1 claiming you're killing his targets for the good of the Republic.
What do you all think?