It now takes them 20 attacks to negate the effect of just the Warmog's, not your own HP. Never mind that Cleaver doesn't give any attack speed or crit chance.
Seriously, building health counters armor pen/shred builds. Right now, Cleaver's broken because they forgot the unique tags, but health STILL works very well.
This is of course a very narrow scope here, and I was rather hyperbolic before trying to drive the point home, but the fact remains that thinking outside the box will allow you to prevail against cleaver stacking.