It makes sense to me that the canonical Dark Urge would be a Sorcerer, an inherently magical being, considering their Origins/Ancestry.
Magic isn't really Bhaal's domain though, never has been. And in life he was a Rogue Assassin. Bhallspawn are conceived through more ordinary means than you'd think...Bhaal assumes the form of a man, seduces, and impregnates some women. If you need another example just look at our dearest sister, Orin...the gifts Bhaal gives generally have to do with stabbing, stealth, infiltration, and naturally, the slayer form. In BG3 Bhaal also gives us a cloak that makes you invisible for 2 turns after killing an enemy...again, clearly rogue gear. Now while the Bhaalspawn in the BG games could be just about any class, and plenty have been other classes, the abilities known to be given by Bhaal himself are typically of a more aligned with what he was in life plus the slayer form.
