I never had a problem managing my pet skills. Especially once you get a rythym down. The only one that's really distracting is using the Felhunter because his abilities often require the most improvisation.
I can't play that game as anything other than a Warlock. Simply the ability to go around yelling "DOOM!" and screaming that my masters from the Burning Legion will harvest their souls when the time of reckoning comes or some other nonsense. I even made a 2 issue web-comic of my homicidal, yet oh so incompetent, Gnome Warlock that I was going to develop into a full story arc before I quit.
He was starting the quest to get some class item ring from a dungeon. He was going to go in, find out the quest giver was a hot night elf, and when she gives him the ring, he was going to mistake it for a marriage proposal. It would have featured drastic differences between his fantasy (with him as a tall handsome human that all women adore who can't be bogged down with just one woman) and reality (with him as an ugly short balding Gnome who is completely desperate).