mantra of recovery
I’ve used this combo and felt it was really worth it. In fact, I think it increases the value of mantra of recovery a lot when compared to the other healing skills. Using it in conjunction with harmonious mantras even gives you 6 condition removals on the charged up if you expend all three uses of it. This allows you to deal with a number of situations, such as having to get rid of an immob buried under a bunch of other stuff, or completely cleansing the effects of signet of spite.
If you’re not using it in a mantra focused build, then it’s possible it may not be worth it, but that will depend on your particular build. It’s possible there may be more effective ways to manage your conditions. However, I’ve run a 4 mantra build in PvE and WvW before that uses the mender’s purity synergy, and I’ve really liked it.