The barrier capping at 50% of your creature’s health means it’s a nearly worthless perk.
Casting Barrier itself via a spell will result in a barrier many times your creatures’ HP values. It’s just not worth the 300+ Perk points it takes to acquire it. The same issue with this perk was present in Sirilim 2 as well.
Now if the Barrier could grow larger per cast and were capped at 50% (or even 25%) of health per spell cast, then maybe it would be worth it.