For those people still wondering:
Talismans are the best catalysts for PvP spells. Their weapon arts will cast the spell and grand you hyperarmor for a fixed minor amount of FP.
Not all talismans offer the same damage and hyper armor, however the Canvas Talisman is the best choice since it's the most well-rounded in terms of hyperarmor and spellbuff.
DO NOT use talismans for buffing, healing or ranged miracles. Yorshka's Chime is WAY better for that. The only selling point of the talismans is their weapon art that allows you to trade even with greatsword users in MELEE range.