I’ve noticed that in leveling dungeons healing wave frequently heals for 10% of what it should. Outside of instances it works OK, but running a dungeon at level 84 it’s healing for like 3K instead of the 30K that it should. Occassionally it’ll heal for the correct amount, but most of the time it heals for nothing.
Going to say no, I did about 30 dungeons to level from 80-90 as Rsham heals. 2 of the dungeons have anti-healing mechs that are widespread amongst normal mobs, not bosses. HW never ‘bugged out’ on numbers unless an event affected it. The only time I saw a ‘3k’ heal was from mobs that applied a health % debuff that can reach 50% reduction on the party. But if you’re right, that is a good call to notice. Essentially, debuff did not allow you to overheal.