I get more kills with support then mid or ADC

Hey,

I'm trying to play with few hereos, i suck with Zed, he's too hard to play, i'm decent with Ezreal, i get like 5-6 kills but with Nami, i get like 10 kills. It is surprising because Nami is a support character but her bubble deals HUGE damage. Maybe my opponents are bad? Maybe their choice of items are bad? Is it normal to have this kind of kill with Nami or like i said i can do it because they suck? I'm trying to understand job of supports in the game.