Despite having the action Vercure, RDM is not a healer, and most RDMs won't have their UIs set up for healing party members. In party play, the primary use of Vercure is as an on-demand Swiftcast when a boss is untargetable, and no serious RDM will cast Vercure when an attack spell is available. Vercure should be on the bar, for this reason, but it doesn't necessarily need to be part of a UI setup that makes it easy to cast on anyone but self.

This should be quite fine in matched Deep Dungeon parties, because they are designed to be completable by any party composition, and if there are four party members, the solution "just kill it faster" should apply without any problems. If it doesn't, one or more party members are doing it wrong, by pulling things they shouldn't or by not knowing the most basic of basics for their jobs (e.g., slowcasting Verslowspells). Even then, one person playing competently should be able to kill a mob before the other person needs healing. You could be the RDM who kills the mob in 2.5 seconds just as easily as you can be the RDM who heals the person who doesn't know how to job.