[Zallar]

Go for Int, like you already have realized the stamina isn't going to give you that much of a difference at endgame and likely you'll spend the majority of your time not raiding.

The two arguments for Conj and Evo spec go like this:

Conj - You spend less downtime when you login or when equipping a group, you can also chain cast pets cheaper.

Evoc - When the shit hits the fan and you need fast nukes, you will appreciate your evoc spec.

Personally, I think Conj is the right choice. Group with the right people and play a smart mage and you shouldn't be in a situation where evoc spec is going to play that much of a difference. Also, The situations where evoc spec is going to be needed are like 5% of your playtime. The rest of the time, it's all conj.