This mob seems to proc Guardian Strike only if your health gets to a certain threshold for the tank. If you are able to keep the tank around 60% health this ability is never triggered from the experience my group has had. We have done this mission 6 times total. We scraped a win 3rd & 4th time, with the last 2 being cake walks. The difference was levels and gear, we had much better gear than our first time through and the tank's health did not drop very low at all and never saw the guardian strike ability.
Edited, Apr 10th 2022 1:08pm by FireNightblade