Storm's Path has nothing to do with this. It's an enemy damage debuff to compare to PLD's Rage of Halone debuff. If you want to compare total mitigation, then I'm going to have to start with that ~12% base advantage that PLD has without any abilities at all, just from blocking and Shield Oath over Defiance (post-buff).
From Doctor Mog's sheet in p3, skill speed reductions with Greased Lighting are multiplicative with skill speed bonuses. It is unlikely that Fey Light behaves differently. You get 0.01 GCD reduction per 10.5 points on average (10/11 alternating) starting with -0.01 at 342. Getting 1.5s GCD with WAR is totally impossible; you would need 712 skill speed. MNK stack 491 just to get to 2.00 at 3 GL stacks.