How is Frozen Mallet + Black Cleaver on low mobility AD Fighters?
Looking at -

I mean the midgame build isn't too bad -

Why aren't they more popular? Or am I missing something?
TL:DR -

Looking at -

I mean the midgame build isn't too bad -

Why aren't they more popular? Or am I missing something?
TL:DR -

Black cleaver is popular on bruisers. The build path for frozen mallet is kinda meh, and it's very situational. There are better items for for all 4 of the champs you listed. Sion doesn't auto attack very often unless you count his death, but that would mean your planning on dieing, which is bad. There is a way better build path for Udyr. Olaf already has a perma slow if you are skilled with him, so there's no need for the mallet. Aatrox build mostly attack items which means he builds 1 or 2 defense Items and frozen mallet doesn't give any resistances, which makes other defense Items better like a GA(since he is squishy) and the magic resist item that boosts his healing.
Try mallet on teemo. Very nice item :)