Its HPs are so low it just kind of keels over when any kind of PC shield goes up... or otyughs / scarabs... or any creature that can plaster it with poison...
Ya, in theory its got nice defensive potential, but its too tissue paperish and / or expensive right now.
Spell damage evasion in general might be nice. I.e. like permanent self - atlantis protection. Then rage nymphs, owls eyes, etc. cant go to town on it either, and it would actually be truely protected from firestorms, dryspells, etc.
At that point you could leave the low HPs as is it would stay vulnerable to shields without being tissue paper.