Yes, HAA deserved more air time - particularly because his scenes with Lara Parker and Grayson Hall were so dicey and fun to watch (and re-watch).
My fave scene was when [spoiler]Angelique was on the loose, "vamp"ing poor Barnabas. Julia Hoffman caught wind of it, brought a stake and mallet to Nicholas' house, prompting Nicholas to wryly comment "A memento of your visit, Doctor?"[/spoiler] Only Julia had the guts to push the envelope with our favorite warlock... well, Angelique did too... but she got a slap across the face for her defiance. Now that I think about it, Nicholas and Julia share the honor of being the only two characters to ever smack Angelique upside the face.