Possibly. I haven't been able to find any Leader-typed Ancients in Derelict missions yet, but here's another from an Invasion - this time a Sanguine (Disruptor) Ancient Elder. Well, probably a Disruptor. This mission hasn't spawned any Toxics or Healers. Infested spawn tables are a little weird sometimes.
Ed: Found another. Sanguine Toxic Elder during an Exterminate Alert. http://i.imgur.com/0lLARhR.jpg
Ed2: Okay, maybe it depends on the prefix? Energy-Leech type Ancient in Invasion, suffix Leader: http://i.imgur.com/Xv6FEXW.jpg