Unholy - Mastery vs Versatility

[Laggasaurus 0]

Something's been bugging me recently - why is mastery more valuable to an Unholy DK than versatility?  It seems to me that versatility should be superior because it increases ALL damage (shadow & physical) while mastery only increases shadow damage.  Does 1% of mastery scale differently than 1% of versatility in some way?  I assume I am misunderstanding something here about how versatility works. 

[Shells 64]

Im going to guess that its easier to get 80% mastery than 80% versa is the reason, the scaling is likely different. 

Mastery also buffs your ghoul and army and DA as well so there is a bit more going on there.

[Vacivity 0]

First of, lets get this out of thew way: Versa buffs all your damagedone, including pets.

1% versa will net you more damage than 1% mastery. However, getting 1% mastery requires WAYYYYYYY less rating of that stat (lets say 1400 mastery vs 3000 versa per 1%). Those are not accurate numbers, but you should get the idea. 

Therefore mastery severely outperforms versatility in terms of damage, since the majority of your damage is shadow. 

[Laggasaurus 0]

thanks, that makes sense