In case anyone cares, this is what I learned about barb mechanics (online wikis are REALLY bad at presenting info so far, probably cause the game just came out):
Whirlwind seems to be more of an anti crowd skill now. It works wonders against regular mobs, especially large crowds, but seems underwhelming against elites/bosses. Maybe this changes later on with better gear/etc.
Deathblow is another skill like that, great against regular mobs because the cooldown refreshes when it kills them, but against bosses, it's just a high damage ability once every 15 secs.
A bleed build seems to provide better "consistent" burst damage against elites/bosses, though it's more challenging (requires much more positioning, movement, targeting, etc). Bleeds (Flay, Rend) don't stack per se, they just go into a queue one after another. So if you apply 3 rends, they will run for 15 secs (3x5), but still do one Rend damage at a time.
So my bleed build is something like (I am still experimenting): Flay, Rend, Ground Stomp, Puncture, Chains.
Flay and Ground Stomp generate Fury for Rend (and flay adds a bit to Puncture damage, and sometimes generates Vulnerable). Chains apply vulnerable much more consistently, and rend refreshes it. Ultimates don't really fit this build, imo, so I am skipping them.
The general rotation is hit Flay 2-3 times and Ground Stomp to generate enough Fury for at least a couple of Rends. Apply Rends, then Puncture. Use chains before to apply vulnerable and reposition high priority enemies.
The damage comes from puncturing serveral Rends and Flays together into one burst of damage. But also from stacking these:
+ strength
+ high crit chance and damage (passive key skill that applies crit to bleeds, bleeds apply slow + 9% crit chance to slowed enemies, crit gear)
+ damage over time
+ damage to Vulnerable
