300 LifeSteal/Auto attack

What are your thoughts guys? I was thinking of a bursty and sustained dmg champion who gets over 100 armor and MR from a single ability that can build in such a way as to get 300 hp back per auto while also having 2.0+ attack speed and a 900 range gap closer and an auto attack reset for double bonus dmg. What are your thoughts?

Fair? Balanced? Jax?