A method and system for controlling configuration of dual connectivity of a UE in a system where the UE is served by a first access node over a first air-interface connection and in which configuring the dual connectivity includes adding for the UE a second air-interface connection with a second access node to facilitate concurrent service of the UE by the first access node over the first connection and the second access node over the second connection. An example method includes determining whether both (i) the second access node is threshold highly loaded and (ii) the UE is likely to engage in a threshold high extent of data communication when served by the second access node. And the example method includes, responsive to the determination being affirmative, forgoing from adding for the UE the second air-interface connection between the UE and the second access node.