Not a 10 box comment, but I love my mage as well.

I can't imagine living without the portals. With my team, I can be anywhere and send any of my team almost anywhere and then summon them back. I love it.

Arcane Brilliance is still a nice group buff. There's no denying that.

Good synergy overall.

Now, having said all that, I can intuitively see where the dynamics of a 10 boxer is significantly different from the dynamics for a five boxer.