A grind lasting nearly the whole length of an even numbered patch wouldn't be an issue, no. That wasn't your initial argument though. You're moving the goal posts.
Outside the arduous grind of the Identifiable Ore step, the relic has never taken longer than a month unless one opts to progress at a very casual pace. Furthermore, you're neglecting odd numbered patches are intended for catch up purposes. It's entirely different to release relic armor that will directly compete with new brand crafted and normal mode gear. This directly pulls people away from queues and purchasing crafted gear outside hardcore raiders.This is assuming the relic set takes less than a month to get. You'd also have to keep in mind that Crafted gear would be getting augmented versions in the odd-numbered patches (See: 4.3, i350>i360 augmentation).
At the cost of equipment. If the relic releases at the same time, per your original argument, this makes the tome weapon poor value. It takes three weeks worth of tomes and sets you back on further gear progression whereas the relic offers no such hindrance. Likewise, being able to increase the relic to i395 invalidates the odd numbered Primal before it even releases. Even with your aforementioned Zurvan example, the i270 step released with him, not before.The tomestone would still have 5 iLvls over both the i385 and the i395 versions of the relic (the latter when augmenting the tomestone weapon). While you'd be able to augment the relic 1 floor before the one that drops Scaevan Esters, The time it'd take to get the relic should be enough for the more dedicated raiders to get one. Not to mention that the 4.5 primal weapon would be 5 iLvls above the base tomestone weapon.
Also, this one can easily be turned around: Why grind for a relic when you could just get a tomestone weapon?
Glamour. That has always been the main incentive for the relics. As I outline later on, even in Heavensward, the relic only ever matched the tome weapon in odd patches not even.
XIV never had a relic armor grind before, thus Eureka is our only frame of reference. Regardless, I'm not the target audience for 24-man raids. At least not on my main. It's intended purpose has generally been for alt jobs. People will be far less inclined to run it repeatedly for one week drops if they can obtain relic armor... which has no limitation. Granted, this is less an issue if it releases later into the patch.You're too focused on the way Eureka works, when XIV has had relic grind before Eureka (even if this is the first one to have relic armor). Besides, have you ever run the 24-man raid to upgrade pieces on your main job?
And yet, that still contradicts your argument. The i210 step was met with wide spread criticism for being too grind-y, which is the only time the relic held the same ilvl to raids weapon; the i240 step released in 3.3, thus impacted nothing, and the i275 step you mentioned came in 3.5a, five weeks after Zurvan EX. Therefore, only the i270 step competed with any Primal (Zurvan). And only during the last major patch of Heavenswards. If they go back to HW... you'll have this precise same formula in terms of ilvl progression. In fact, let's look at the Midas tier.And that's how the grind should be. The way SE forced the relic grind into its own instance was a mistake, and I sure hope the 5.x relic will go back to how things were in ARR/HW.
Raid weapon: i245
Tome weapon: i230 (i240 augmented)
Relic: i230 (released five weeks later)
Sephirot: i220
The above isn't what you proposed in your initial rebuttal. You wanted relics released at roughly the same time whereas in Heavensward, Sephirot and crafted/normal gear went unopposed for five weeks before you could even start the relic step.