Both Affliction and Demo do that. Honestly all three specs are more than viable for leveling and dungeons it really boils down to your preferred playstyle.
Affliction does gain the benefit of siphon life on mobs but with the change to fel armor (restores 2% of health every tick) you will be more than fine as demo or destro.
If you have good gear I would go Demo or Destro tbh because you will be melting everything in your path. But like I said all three are so close together its not going to make a huge difference. Personally I prefer destruction.
Two taps and I’m back on track. The new fel armor is the equivalent to having a voidwalker sac buff at 70 and combined with soul leech is more than enough to keep you mana’d up.