Pvp/Pve Mage spell empowerments. Need some advice~!

[StevieRae]

Hello, I am curious on what spells to empower. I read numerous guides on Mages that say add:

5 points on MM CD
5 points on Fire bolt's CD/power
etc.. But, I'm curious on the following empowerments:

Obviously, 5 points on Magic blast's CD and power.
Fire ball's Power and CD.

Are those two empowerment options lucrative? or just a waste? In the several mages I have tested, MM/FB empowering, MM especially, aren't as useful as the guides say.

Other questions for you guys are:

Is Magic missile replaced with Magic blast at 49 totally? or should i still use it post-49?

When you acquire the spells in 5x, should you replace the cousin spells, or keep using them as well?

Thanks for your input, guys. ^^