+natural resist doesn't give a resist boost
+iron skin doesn't give a defense boost
+increased speed doesn't give increased velocity
+sword mastery doesn't give increased damage or more critical hits
+any other skill that says (barbarian only) will not make the barb merc use them, or benefit from them in anyway
All this EVEN THOUGH Blizzard states barbarian mercs are "real barbs" (their excuse to enable barb helms for them).
All in all, they only benefit from "all skills" or passive oskills (such as critical strike on Insight, though they can't use polearms...)
Personally, I find act 5 mercs boooooooooriiiiiiing and blizz could have done SO much more with them, like
- Instead of giving them different auras, give them different weapon masteries
- Swords
- Maces
- Axes
- Spears
- Polearms
- Throwing
NM barbs could use shields as well, but have (much) lower resists and attributes
Hell barbs could dual wield weapons, and have even lesser resists and attributes.
Going totally OT here, I'd like it if blizz made it so you'd have one of each merc, but they were unable to go outside of "their" act. That way, you'd have a little more storage, and you'd have to do without mercs in act 4... Not to mention all the fun it would be to equip 12 different mercs! (don't let them travel difficulties either). It also would give some meaning to blood raven and gidbinn quest rewards.