Maul was a Sith Lord. That's all. Warriors, Inquisitors, Juggernauts, Marauders, Sorcerers and Assassins are all elaborations after the fact, made for game purposes and not applicable to the films.
Classes get what they get. I wanted an astromech for my Consular, rather than a Trandoshan. Well, too bad for me. Knights get the astromech, not Consulars. It's pointless to fret over these things. You look at the pros and cons, and go from there.
Want to dual-wield? Go Sentinel or Marauder. Want a double-ended lightsaber? Go Shadow or Assassin. That's just how it is with character classes in SWTOR. Maybe later, we'll have the opportunity to expand our proficiencies. For now we don't.
You pay your buck, you ride the ride. That's all.