The stacks coming from combo counter gain is means you have to drop your combo counter t regain it. reflex means every slam is 5x of the 30 and an addition 7X of regular swinging. So heavy slam proc afflictions. slap, slap, slap, heavy slam. when you are at 30 stacks you could probably just heavy slam everything.

if you want to use heavy slam for the quick gain , drop gain you can replace it for influence and remove heat for electric. or you can use the corrosive one for the corrosive damage

but the slam does have a forced lift which is great for affliciton.