Monk overheal a LOT. Its prefectly normal, because of how Renewing mist and Uplift work. 40% overheal is actually low, I usually do more than 60/70% on every fight. Dont worry about it, despite what people say. If you manage to heal the raid and not be oom, overheal shouldnt even be discussed.
Regarding AOE spot healing, you pretty much got it : SCK spamming. Use Rem, SCK and Expel harm to generate Chi, and spend the CHi on Uplift. You could also consider Chi burst but I believe Uplift is better for 10m format.