Posting a Peach on the Guardian Angel any ability I didn't comment on is fine IMO.
Guardian Angel notes:
Second ability: Does this count as power attack? As in do feats like leap attack stack with it? The wording is somewhat unclear.
1st Ability: Wouldn't the first ability be clearer if it just gave all bonded creatures within 100ft precise shot?
2nd Ability: You might want to introduce a scaling cap instead of just a flat cap of 8 creatures. Not too crucial but I feel the ability to get +16 to damage and to hit at level 7 is a bit too strong.
3rd Abiltiy: What is the limit for things that help ranged combat? Does weapon focus (Longbow) count? Would two weapon fighting feats be granted if the Guardian Angel is dual wielding crossbows?
2nd Ability: If the guardian angel pins the weapon does he still take half of the damage? Also as a side note this ability can't be used on ranged attacks or spells as they don't threaten any squares.
3rd Ability: Nothing wrong with this I actually find it a very interesting and well thought out ability
General: What was your reasoning for including this path? It seems somewhat out of place. Also it might need a different name. It really isn't about stealth its more about coordinating with allies to deal sneak attack damage. Thats just IMO though.
2nd Ability: For when an ally casts a beneficial spell that affects multiple opponents part, does the Guardian Angel and the bonded allies need to be within range of the spell? Or are they just automatically affected.
3rd Ability: The extra damage can make low level fodder mages incredibly lethal. Assuming the Guardian Angel takes leadership by level 20 and either has an ally that can cast 9th level spells or a cohort he can inflict an insane amount of damage with this ability. Might want to make it deal 1d6 divine damage for the individual spell level not the highest spell channeled in a round.
Vengeance: Incredibly broken and exploitable for this reason, you can bond it to animals. Keep a 1 hd rat or something you are bonded to near you. If you ever get hit with an AOE you get a permeant auto crit effect on them. Or you could bond with a spider and control have it walk on the enemy who will crush it and gives you a permanent auto crit effect. Not sure how to balance it but it is easily exploitable in this form.
Vengeance II & III: Same as above.