Since both chars are Lone Wolf you can invest quite a few points into Bodybuilding and Willpower early on.
As long as the 2h berzeker runs free it's all good, and the support mage can help him get free. Wildfire if he's frozen, or just oil him and a nearby enemy to set them both on fire (and unfreeze).
You can get knockdown immunity later on. Anti-fear & charm from traits and stun immunity from lightning shield, etc...
Or CC their CCer first. Plenty of counters overall.
Perception helps a lot to reduce long range misses. A few points is pretty vital. As well as Bless or the +30 hit stance.
Oh and as far as Lone Wolf & Glass Cannon go, I made a
comparison of the two talents and how they interact with eachother on medium and hard.