Can effectively block enemies from reaching you in certain situations. Cast on narrow pathways or in dungeon hallways and enemies will often lose interest or run in the opposite direction, bewildered.
The bronze and silver Barricade mods are highly recommended.
The chance to reflect from the Vengeance and Runes mods applies to attacks that hit the barrier, not the Dragon Mage. However, it is rare that an enemy will actually try to attack the barrier. Most ranged enemies, if they cannot hit the Dragon Mage, will either look for a way around the barrier, or just stop attacking. Therefore these mods have limited usefulness.
With the Solid mod it's easy to get the duration of the barrier higher than the cooldown. However, the Dragon Mage cannot have multiple barriers up at the same time. The old one will disappear when the new one is cast.