synergies only work a) on the same character and

with hard skill points
the 'prayer' merc (aka A1 combat in D2L) has prayer as his main aura which is interpreted as a regular skills. thus any aura granted by items he wears (!) will receive the synergies, this holds for cure helm (cleansing) as well as insight weapon (meditation)
you can use the same mechanic on your own char: skill prayer and wear those items to receive the synergy effects