Under performing Mage in my team

[Deleted]

All of the above mentioned tips are correct.

But id like to pitch in with actual method to help your mage be a better performer.
Ask him to try to do proving grounds endless wave 30 or at least work on it. It had a massive influence on my learning process when i was currently learning frostmages. I swear that if he manege to pull it off, his powerlevel will go over 9000 and be a super saiyan.