Jack_B97, a Warlock could be anything, if you think about it, there's a mages guild rank called Warlock, iirc.
I think Sorlin's class is good for what he wants to do.
If you wanted to go purely by game mechanics, there's actually a Warlock NPC class, and it has the following attributes and skills:
Governing school: Magic
Primary attributes: Luck, Willpower
Major Skills: Athletics, Blade, Destruction, Illusion, Restoration, Acrobatics, Light Armor
So it's set up very much like what I'd consider a Nightblade or stealth Battlemage.
But that's just one interpretation of what a Warlock is. In Morrowind they used blunt weapons I believe. A lot of these NPC classes are open to personal modification.
Choose whatever race suits you best. Both have strengths and weaknesses. I lean towards Dunmer myself.