i have bonded 2 vollems to my mage. since I have no taming, the vollems are amazing, and way tougher than anything I could summon into the follower slots anyway. If you have taming, then dont bother breaking them out of the crystal, you wont think they are worth the space.
For a non tamer they rock.
I can walk into a gang of 5 litches without sweating now.