Oh, so I guess Ausrine doesn’t really require going around it like ToS Base said. I apologize, I guess all the more reason to say that ToS Base just won’t answer every question for this game…
About Carve Owl, I’m actually refering a bit on late game use. Here’s a video example:
Barrier spam (scrolls or paladin) is common in Earth Tower, and there is hardly any way for a Monk to deal DPS with Double Punch or you risk dying, hence Owl Carve will serve you well. Of course Carve Owl is a given that it can take aggro by attacking monsters, and help a lot on AoE based damage which the Monk severely lacks.
As for Safety Zone, the +1 block attribute per level is unlocked only at c2. The problem with World Tree is that it will not help against bosses, and bosses that deal multiple hits will break down your safety zone quite fast which will leave you and your party members almost defenseless (unless you have Ausrine, of course). This is why I appreciate a good, solid Safety Zone, that way I’ll be certain that so long as the magic circle is active and the boss doesn’t have too much of a multi-hit attack, I can stay safe and deal DPS.
Honestly I’m still not convinced with Priest c1 at all though. Resurrection, while nice, will not remove the penalties that come with dying. People can also walk back to where they were anyways. Blessing will not provide much use late game. However Monstrance and Aspersio are indeed decent, but I don’t think it will impact late game that much as compared to 10 tile heals, Fade or Divine Might. I suppose it’s not my cup of tea, but we do have different viewpoints on this matter I guess, and so we should just pick whatever we like. 
Also correct me if I’m wrong but… If you’re going cleric c1 -> priest c1 -> Deiv c3, wouldn’t you only be able to get Monk c2? Or if up to C2 Diev only, you would lose out on Ausrine which would help a lot without c2 cleric. Or maybe you were talking about a non-Monk build. If it was, then Monks can’t take both Priest c1 and Diev c3 because we’d lack 1 rank for Monk c3. At most, it would be priest c1 and diev c2.