Anecdotally, I ended up grabbing Tal'sana (Level 3 Shadowblade) to fill my fourth slot. She's simple and streamlined, which aren't traits you find with most of the other Henchies at the moment. +2 Single-Handed, +1 Scoundrel, +2 Witchcraft. Her Traits are Bully, Elemental Affinity, and Know-it-All, and her attributes are spread pretty evenly between Dex and Intelligence.
That's the kind of Henchie I like, because they start with a solid base, and I can quickly build them toward the sort of character I want them to be (in this case, a crowd controller who can hinder foes, then finish them off while they're prone/stunned/crippled). The only issue I have with her is the fact that she has Elemental Affinity, but no points in Elemental magic - but that's not much an issue for me in this particular case, since I plan on giving her a few points of Earth magic (for the summon and the oil spell).
I do miss the personality that comes along with having a proper Recruitable Companion, though. But for now, Madora is making up for that. Still, I'm eager to see what other companions Larian ends up adding to the game in the long run.
