Alexstrasza & Sabellian both have a harem. That's normal for dragons. But what is bothering people is the quest treats Malygos' "madness" as something completely outside of his character, like Sindragosa turning undead. Without further exposition they don't explain why is Malygos's villain arc something that doesn't reflect on his character, but for Neltharian, it absolutely does: Both in 10.1's questchains and the characterization of his Simulacrum in the raid.