With his skills so wacky by default I couldn't even guess what runes will do to them. That's one of the reasons I will be playing a WD first. With the other classes I can kinda see the possibilities. That's not the case with The Doctor though. He's a mad man with a box... without a box.
I have one idea for Soul Harvest though. The devs stated multiple times, that they don't want summons to be able to kill monsters efficiently by themselves, but I think they could change Soul Harvest in a way to allow this without the gameplay becoming boring. They could change it so that it would favor builds focused on summons by giving bonuses to pets instead of the WD. The strength and duration of the buff should depend on the number of enemies around the WD when he uses the skill. This way a summoner WD couldn't stay safely behind his minions while they kill everyone. He would have to take risks if he wants to use his pets efficiently.