Not sure if this has been reported before, but while having fun with Brachina beetles I located a lvl 121 beetle with only 20 hitpoints, also did it only require a Dragon’s Reach to effectively kill it.
I however did receive 24424 experience for this lvl 121 beetle, while killing a lvl 119 beetle only a few moments later had 9500 hp give or take a few and gave 22174 experience after death.
While I have only located this phenomenon once I will keep my eyes open.