Coven Sub-Alignments other than Coven(Evil) should be added. They help differentiate the roles between each other, and what they should be doing. Mafia also has them so I don't see why Coven roles can't either.
Coven(Killing): Coven roles that's main ability and/or goal is to kill. (Poisoner, Medusa, Hex Master)
Poisoner fits into Coven(Killing) because, killing is the only thing they can do. Same goes for Medusa. Hex Master can frame people, however their main goal is to get the hex bomb, or kill people with the Necronomicon.
Coven(Tactical): Coven roles that can be a jack of all trades. (Potion Master, Necromancer)
Potion Master fits into Coven(Tactical) because they can heal, reveal, and kill. That's 3 abilities, making them a very tactical role. Necromancer fits into the alignment due to them being able to also kill, reveal, and heal; it all depends on the roles of the dead.
Coven(Support): Coven roles that's main ability is to gain information for the faction and help them defend against others. (Coven Leader)
Coven Leader can kill with the Necronomicon, yes. But their main power is controlling people, which is why I think they fit into a Coven(Support) alignment.