Chaos blades vs mastery stat priorty?

[Shieva 0]

I'm currently at 854 ilvl on my Havoc DH, with stats around 43% crit, 5% haste, 18% mastery, and 7% vers. According to Icy Veins stat priority, I have way more mastery than I should, however, mastery is required for the recommended talent Chaos Blades. Why exactly is mastery not valued much at all when it's essential to one of our main talents?

What exactly should my stat distribution look like, assuming I'm able to find gear to replace the high mastery?

[Valks 2,375]

Mastery may help with the scaling of Demon Blades, but that's 12 seconds of every 120 seconds. There's no point stacking Mastery for that tiny bit of time, for a small increase in damage. The cooldown is already solid and better than the other options in Single Target, so there is no need to try tailor our build around it.

The other stats outperform it in the other 90% of the fight and some even do during those 12 seconds.

There isn't a perfect stat distribution to aim for. You simply aim for as much Crit/Vers as you can.

[oddbods 0]

I don't understand how versa can be better than mastery, since 3 out of 4 main abilities is chaos damage?! AND Chaos blades scales with mastery! 

Let's say you have 5000 mastery or 5000 versa! You would get more damage with mastery

So PLEASE explain to me why versa it better

[Saphirro 1]

simple. versa increase overall dmg meanwhile mastery just chaos dmg. u boost 4 abilities with mastery +12s every 2 min or u boos your whole kit, yes including AA, forever.