Improving Zigg's passive for the better
I feel like Zigg's passive doesn't match is "high range, AoE, barraging enemies with a spray-and-pray of bombs" gameplay.
My first thought is, have the enhanced auto attack reduce the cooldown of his Q buy a %? It would make sense, the name being "Short Fuse", this way he can maintain his long distance poke game, but if he's close then can go all out with the bomb swinging and flinging.
Logic: Last season, Zigg's was compared a lot to Xerath, but eventually Xerath won out as Zigg's bombs were nerfed with the trigger range; this will help his gameplay, as they can both be still similar, but the cutoff is that: Xerath, with very simple skillshots, is taking consistency over Ziggs, who has very erratic gameplay. But now, in theory Ziggs can pump out a little more damage with a wider room for error, that Xerath doesn't.
Edit: I'm not removing the damage from the passive; only adding this bonus cooldown effect. His bombs are hard to hit, at a lot of levels of play. Even getting the spacing right is hard, as they will go either go close or far, and under a lot of circumstances the former is not as impressive a help to hit. This would help while also keeping the rest of his kit intact.