The Udar seems fairly underpowered as artillery piece considering the lengths the player has to go to in order to acquire one.
I directly compared the blast radius and damage of the Bulldog to the supposedly tier three Udar and the tier two vehicle easily came out on top due to the Udar's gun literally behaving exactly like a mortar, complete with poor accuracy and a pitifully small AOE.

The only advantage the Udar seems to have over the already technically portable mortar (which can even be loaded onto any other vehicle for transportation) is that it doesn't require reinforced barrels.

In light of all this, the udar should probably be buffed compared to the standard mortar to have more damage, AOE, and accuracy, provided their is a second gunner.