So Spirit Visage gives +25% Healing for Healing items, Technically Life Steal is something that can heal so does it work with Spirit Visage? Btw Plz don't spam with downvotes its just a quick question I wanted to ask.
Dude you could've just asked me, I've answered your questions before and ended up adding you.
Yes, it works, because Spirit Visage increases ALL healing by 25%.
yes
So would it benefit an adc with a bloodthirster or qss to build visage as a last item?
http://leagueoflegends.wikia.com/wiki/Spirit_Visage
"UNIQUE: Increases effectiveness of all sources of health restoration by 25% (including health regeneration, life steal and spell vamp)."
Just read the item, mate.
Btw, this also means you get 250% base health regen off this item alone.
It was this way for a while (not sure if it still is) but if you looked at your life steal stat in-game spirit visage would just update the number. So if you had 20 from 
it would display 25
Yes it does; tested it before & after it's changes.
yes
