Rework the Life Gain on Hit gem.

Simply put, there's rarely reason to use Life Gain on Hit beyond the early game. Life Leech on its own generally provides more health, is usable with spells and secondary damage, and when combined with Vaal Pact or Acuity provides more instant health than LGoH. Not to mention Life leech only has a 130% cost multiplier to LGoH's 150%, and supposedly Vaal Pact is going to be better in 2.0.

So, rather than trying to buff the health values to compete with Life Leech, how about giving LGoH something Life Leech-VP can't provide: mana gain on hit. Make it about 1/3 the magnitude of the life gain values. Life Leech would provide better health sustain, but LGoH would also grant a degree of mana sustain as well, giving it more reason to be used.

life gain on hit already does 2 things life leech will never do

it gives life when you hit stuff with 1 hp left but affected with the "cannot die" or "cannot be damaged"
life leech will not work in those instances.

also it works based upon the base damage of the skill itself. so heavy strike for example will increase it with 150% and further reductions with things like splash do not affect it.
LgoH numbers might be small but if you hit 10+ numbers it is usually enough to keep you alive.

also its not affected by your damage output so its FAR LESS dependent on gear.

i say its perfectly fine.
"don't fix whats not broken"

It's useful with skills like Lightning Arrow and Barrage that hit a bunch of times for smaller amounts of damage. Frankly, any AoE build that has fast attack times will benefit from LGoH. It also heals instantly (if I'm not mistaken? Correct me if I'm wrong here) whereas leech does not, and leech rates are apparently going to be nerfed massively in Act 4.