ilvl doesn't matter until endgame basically. 120's have some hidden scaling in pvp, which is wonky as hell. Basically, high ilvl people will hit low ilvl people for less. The damage that is displayed client side is different for both individuals, so you can't even properly test this without actually screen sharing. So at endgame, you might hit someone for 13k on your screen, but on his he only got hit by 8k. And this is retarded, because it makes the player unable to analyze his own damage and expectations.
And there are people abusing this at endgame, wearing super low ilvl greens with socket gear etc. playing heavy dampener comps, where the win condition is outlasting, and "playing not to lose", rather than "playing to win". Absolutely disgusting.