Since the Sept 29 patch, ranger spirit buffs do not prioritize player characters.
Before the patch: Spirit buffs would be applied to player characters (and team members) first before any other entities (Ranger pets, other spirits, NPCs, etc.)
After the patch: Spirit buffs are applied to any entity around them, including other spirits, ranger pets, etc.
Problem: Due to the 5 target cap, this causes spirit buffs to not be applied to all party members in a 5 person group. This is especially true if you equip 4 spirits (i.e. Water, Frost, Stone, and Storm). In the worst case, these 4 spirits will apply buffs to each other first then to 2 other entities if in range, instead of your 5 person party first.