If you pick hollow lich then you will not be able to leech at all because all of your leech is converted to damage that includes items, passives, idols.
You would want to take Hollow lich if you are using Exsanguinous or Shroud of Obscurity unique chest to use ward as your health. However ward was nerfed this patch so it is not as strong as health + health leech atm for lich at least.
One quick note,all other forms of Healing, HP Regen and Health on Hit is still working.
So the best synergy if you wanna take it and still have some form of sustain is Harvest Node that gives you HP on hit equal to your INT, which also scales pretty well if you are going for a Max HP + Ward hybrid build.
HP on hit is per hit. So if you have an AoE skill (eg, Devouring Orb or Shield Throw with the Eruption node), then you will get 1 lot of hp per mob hit.
Basically every “on hit” effect counts for each enemy you hit with an attack.
And in my example Harvest is a great tool to utilize on hit effects of all kinds, because it is inherently pretty great AoE and can be specced for even greater AoE.
In conjunction with Lich Passive Tree Node Darkguard(up to 21 Ward on Crit) and some Harvest Specialisation Tree Nodes, that give Crit and Ward you have a solid foundation for a facetanking melee lich.
This was always the playsytle i enjoyed the most with Lich.