I wouldn't completely rule this out, but my test mobs ranged from R1 to R44 Cactuar Jack and everything seemed to be in proper order. Also I would point out that if you take a GLA and THM out to an R58 mob (Ifrit's level), the GLA has a MUCH easier time holding hate than on Ifrit. Not saying Ifrit is an 'exception' because of that, but I would be surprised if the answer was simply mob rank.