Elemental Shamman PVE - A small big doubt

Hello everyone. I've been trying to play with a shammy for the last couple days and even knowing that it is kinda low at dps atm I want to stick with it for a while. My doubt is - the guides over the internet sugest that I should go for Haste for a linear DPS increase. Some people in-game told me that I should go 50/50 on Haste and Mastery and recently even one player told me I should stack Mastery as much as I can.

Now the question is - which one is better? I know that haste will make me cast lots and lots faster, but wouldn't the mastery be better, since I would have a big chance to send another spell? Give me your opinions and let's make the elemental shammy revive themselves.

It all depends on the tier set bonuses that are you wearing
If you have none - go 50/50 mastery and haste.
If you have t12 4p bonus, go full haste, because more haste - more instant lava bursts, which is extremely good.If
If you have t13 4p set bonus, go full mastery, because if you go full mastery you get a lot of overloads, which allow you to maintain a high uptime on the haste buff.
And as always, crit sucks

Froeltheshammy is correct but it even goes further than that.

Not only should you be going full mastery once u have t13 4p, you should be going full mastery the very second you set foot in dragon soul.

You should really sim your gear (EVERYONE SHOULD SIM!!!) because once you have basically 380+ ilvl, you should go full mastery and never look back.

On my ele shaman (400 ilvl) the delta plots in simcraft are still telling me that I can reforge another 531 haste to mastery and still gain dps.

Thank you very much for your answer. I'm still undergeared (379 iLvl with a cloak 333 and vicious shoulders) but yeah, I understand what you're saying. Thank you ;)