Cleave does 70% AP for 20 rage and slam does 35% AP for 20 rage.
Even with the slam talents – 60% increased damage and 15% increased chance to crit for a total average increase of 1.84*35= 64.4% damage cleave does more damage per rage. So of you pick up cleave do you just replace slam with cleave?
Also, it seems like barbaric training – 30% increased damage to slam and we is a trap. Because it also increases the rage cost which drops both of their damage per rage.
I have tested replacing ww and slam with cleave in aor and single target – maybe I will rage cap too easily. But if cleave does effectively replace both it seems like a design flaw. Not that I would mind a simple arms rotation. I would love for cleave to be core in single and aoe.