actually... i find it not that useful... as most ranger use kindle arrow which turn their bow dmg to fire... they no longer use piercing dmg... so out of 30-50% of all ranger dont use kindle... and out of 6 classes, there aren't that many rangers to meet comparing to the chance you meet a caster.
If you are not going to pump tactic pass 12... don't use it. Just purely focusing increasing your general armor is alot more helpful comparing to this.
The quick recharge and party based % protection against projectiles make this an underrated skill IMO. AFAIK 'projectiles' are arrows and any other arrow-like attack (the devourer's attack etc.) - i'm not sure whether it applies to wand attacks as well, i doubt it.