What kind of state is Frozen Mallet in right now? Should it be tweaked?

I can't remember the last time I built one, and have no idea whether it's strong or underpowered right now.

Still, I look at the item and I think "automatic slow on basic attack with wonky counterplay". It makes me wonder if the item would be healthier if it applied a stacking slow instead of an instant heavy slow (thus allowing more power due to higher counterplay).