Ok so i'm just curious as to how this works, if you get 
,
,and
you have 42% lifesteal but if you add 
with the right Masteries you have 55% Lifesteal which is the cap limit. So what im wondering is if 
and 
would give me the unique passive of 15% lifesteal so that ill have an extra 30% Lifesteal?
MisterHealYoGirl3 votesDeath's Dance's passive is unnamed, so yes, the two stack. Lifesteal has no formal limit, though; I believe the maximum is around 230%.
TheBLTK1 votesI just played as 
and it capped out at 55% but im just curious cause if it works that means ill be gaining around 85% Lifesteal
Sneakyy XD2 votesThere is no cap to lifesteal.
Death's Dance and Gunblade do not give lifesteal
TheBLTK1 votes Unique Passive: heal for 15% of damage Dealt .
Unique Passive: Dealing physical damage heals for 15%.
67chrome1 votesThere isn't a cap on life steal.
There are also champions in existence with %life steal steroids in their kit than can easily break any artificial cap certain item builds bestow, so highest life-steal possible is dependent on being the champion with the best steroid of such types.
Also worth noting a lot of not-technically lifesteal sustain exists. The vast majority of fighters and tanks in LoL have some sort of self-sustain buff. Sometimes it's a minor HP/5 thing, sometimes it's life-steal, sometimes it's stronger than life-steal.
Throughout the years max life-steal has fluctuated a lot. With pre-rework Sion his rank 3 ultimate offered 100% life steal, and with season 1 Bloodthirster's you could stack those for 25% life steal 6 times, for a total of 250% life steal.
Finally: 
's passive modifies you're total life steal and spell vamp, increasing both by 30% (along with any other effect that's essentially life steal or spell vamp: like Death's Dance). SV also updates all life-steal/spell vamp numbers on your GUI, and if you're interested in sustain: it does bolster HP/5, self-healing, support heals, healing potions, health relics, fountain healing, and anything that restores your HP outside of directly increasing your HP pool.
TheBLTK1 votesI never thought about using that im gonna try to fit it into my build and see how well it works thanks