Maybe it is just my imagination....which I highly doubt after killing around 200 while farming legendary loot midgets...but this species seems to have a bugged balancing. His shields seem to go down faster, than the ones of normal stalkers and the same goes for his health. All in all he seems extremely weak compared to other Ultimate Badasses.
Ya know, I've noticed the same thing. Ultimate Badass Stalkers always seem to die super fast. I used to get worried when i saw them, as I do with most Ultimates. Now though, it's like "Oh look, the joke of the Ultimate Badasses", and then i just mow through him. Not really sure why that is though.