There hasn't been a relic grind in FFXIV that's been too grindy for me—Eureka was grindy enough that I only wanted to do it once (as opposed to previous relics where I've done multiples), but I was still more than happy to do it (and had lots of fun doing so).

I'd be completely fine with grinds as lengthy as FFXI's legendary weapon grinds (with the caveat that the weapons should have upgrade paths available such that they can remain relevant for years, not just the last few months of an expansion).