Brother Xavier is a bit weird. Why would I want +1 in a Guardian card in my Ally slot? And he can soak up other investigator's damage. And if he's discarded he does damage, a bit like a Beat Cop (0)? What kind of strange combination is this?
Yet the thing is ... he's really good. That +1 helps an investigator like Roland or Skids avoid sanity damage from the encounter deck. 3 health / 3 sanity is awesome, and he can tank for anyone in his location. And should things get desperate, and you find yourself in combat, he can use all his health and sanity and then do a meaningful amount of damage to get you out of trouble. In short, he's awesome.
I think Brother Xavier is actually better than Beat Cop (2); only slightly more expensive, cheaper in terms of XP, and can do as much damage. Beat Cop only wins if you really need that +1 combat, and can live without that extra sanity and willpower...