Thunderlord's shouldnt proc on a single ability cast.

I've been playing a lot of the Donger recently, with a lot of success.. maybe too much success...

Donger has always been great in solo queue due to how well he punishes sloppy engages(which, in solo queue is every engage), but thunderlord's on him seems almost abusive. It is possible to proc thunderlords's with a single W cast, as long as at least 3 rockets hit the target, making his early poke hit extremely hard even with only 1 point in the ability.

My understanding of thunderlord's is that it is meant to complement combo casters and assassins who rapidly use a full rotation of spells on one target. Right now it complements almost everything due to how easy it is to proc on nearly every champ. I even saw a using it, who was perfectly able to proc thunderlord's with a single spiritfire, as long as I took 3 ticks of damage from it.

Seems like common sense that thunderlord's should only get one stack with any given ability cast, even if the ability can hit multiple times. This would at least help push it back into its niche of combo casters, rather than being a practical pick on everything.