I'll add in another means of stopping the bleeding, then.
Except I don't want it to be an armor bonus. I want it to be a deflection bonus, because that defends against touch and ray spells and doesn't stack with a ring of protection. it's also supposed to represent not wearing armor so that people can check out your body better and thus have trouble hitting you.
The wording was lifted directly from a demon prince entry, so if it's awkward, it was written awkwardly by WOTC first.
The problem with that is that they will never be selected in a game that begins above the level when such enhancement bonuses are easy to buy (i.e. 6th level or so). I created them because I wanted to make them appealing choices to warlocks that were being created at mid to high levels (which most of the Least invocations are not); lowering them to a fixed +4 eliminates the main reason I wrote them.
Also, all of those ones you mention have an additional effect beyond the second level spell they mimic. Spiderwalk makes you immune to webs, Baleful Utterance dazes and deafens a creature holding the object, and See the Unseen gives you darkvision. Making Hezrou's Endurance just a fixed bonus would actually make it worse than other Least invocations.