Re: Sword and Axe Barb
As a rule of thumb, when making a pure build, it's obvious to fill out a single mastery to get the maximum damage, but making a hybrid almost requires a max mastery to do enough damage to make it work. That said, using two masteries, such as axe and throwing for Frenzy and Double Throw, respectively, never needs more than ten into each. So, I've come to the conclusion that no more than twenty points combined should be spent in weapon masteries either way.
Though ten into Sword Mastery and ten into Axe Mastery should do the job, what's the point of two? Think about spending ten skill points, which are limited resources, on aiding that other weapon in your off-hand. They don't benefit you in any other way and you already gain the exact same bonus to another type of weapon. It makes more sense to ask what a proper companion weapon to either Azurewrath (1.10) or Death (war spike) would be, and that's considering the runeword in that weapon is suggested.
I'd suggest one weapon mastery, maxing Double Swing for higher attack rating overall without the nuisance of using mana, having at least one point into DThrow for some range, and having a place for the extra two points after Shout is full (you spell out 108 points). Just remember that DSwing is used more like Stun is, but for dual-wielding, in that it only gets enough damage to leech from and is mostly used for infliction of non-physical (elemental, poison, etc.) damage on multiple targets. If you're expecting the damage from Death to be better in an axe than a sword when you're using it with DSwing... well, you'll be in for a shock.