My suggestion for fixing parry as a stat is to have it also reduce the cool down of job native mitigation and attack abilities by X percent per point. Meaning stacking parry would give you a random mitigation increase and a calculated damage mitigation decrease over the course of the fight, along with a slight increase in native damage cool downs for tanks. If stacked heavily it could allow for extra cool downs available negating the use of living dead in some cases, while also increasing the rate of proc and ogcd abilties like reprisal, fight or flight, mercy stroke, dark passenger, etc. by effectively lowering their down time. This would offset the loss of damage associated with the opportunity cost of taking parry over a damage stat like crit or det and actively incentivize its use.
With the recent overall reduction in tank damage due to tank stat normalization this idea could be applied without disruption to the general relative balance of tank and dps damage output differences.