I have seen a Jhin heal for over 1000 with a warlords proc

Video please

So he had 1000 AD then?

That would require 1000 AD and Infinity Edge. While certainly possible, he likely had some lifesteal as well.

i've seen jhin do over 1400 damage on jungle monster on auto attacks in lcs.................

so, if you add warlords and 1-2 life steal items. he can heal for a shit load in late game. But he still only has 4 auto attacks