Firestarter Proc:
Proc from Fire (Purpose to deal damage)
Able to instant cast/no mp Fire III (purpose to deal even more damage)

Straighter Shot Proc:
Proc from Heavy Shot (Purpose to deal damage)
100% crit on next Straight Shot (purpose to deal even more damage)

Sacred Soil Proc:
Proc from casting Sacred Soil (MAIN purpose is to mitigate unavoidable AoE damage)
Next Succor 0 mp Cost (After the major damage has landed, succor for 0 mp)

Overcure Proc:
Proc from casting Cure II (A powerful single target heal)
Next Cure III (an area heal) half mp cost (?????????????)


As observed from the above 4 items, majority of the procs (I don't dare to say all, as I am not sure :P) have great synergy between the 2 related spells, except Cure II and Cure III.

There is no smooth transaction between using Cure II, proc-ing Cure III, and using Cure III.

Given the proc chance is 15%, and the proc itself last 15 seconds only, you need to have all the stars aligned (your cure II proc and the next big unavoidable AoE is gonna happen in less than 15 seconds), to even enjoy this proc. The chance of this happening is abysmally small!!

Please increase the duration of the proc (to infinity and beyond if possible), or drastically increase the proc chance of Overcure to improve this trait for White Mages.

TL;DR : WHM Overcure Proc has 0 synergy between the 2 related spells, a change is required