You don't always know that you're doing damage, hence the reports-- which is the healthbar's state at the beginning of the round. The health bar is read in two parts: the blips underneath represent the number of full health bars that need to be destroyed, and the percentage is the length of the current health bar.
The second part is a little harder. One blip on the left side is 1/20th of the bar's length. Two blips equals 10%, or 0.10. Once you have some practice eyeballing the length of purple, you can report the percentage more easily. Sometimes my MK rounds show nothing, sometimes the healthbar falls up to four blips. You never know exactly how much that could be-- because ultimately damage is uploaded to the dragon when it says "Accessing server".
There is also the problem of far fewer players in general fighting him (not that I expect my contributions to mean a lot in the big scheme of things). My personal schedule does not permit me to fight it as much as I would like.
That said, I am still having a huge amount of fun fighting the online Ur. :D