Glory Callers are both the support and damage soakers of the team. Their main role is their one shot ability to force a unit one space, giving you a virtual extra movement, allowing the unit to reach further or just in general help a faction that is highly based on formations and positioning to achieve their goals.
After that trick is used, you are left with a 4 life body that can be used to protect spots and cover Shale Slingers, and with Sunderved’s support they can do some damage if needed.
All in all you should think of the Glory Caller like an event that forces a unit one space, and then leaves you with a cheap body to be used as a damage soaker.