The SSR grail is a TERRIBLE usage of the draconic eye shards. Why? Because its effect can be replicated in, frankly, far far easier ways without the associated opportunity cost.

Consider this, the most 'points' you'll ever need to guarantee a skill level up is 380 (when you try to get an SSR weapon's skill from lv 19 to 20, which is the level cap).
An SR weapon (not even the SR grail, but any leftover SR weapon from disaster raids or from the gacha in a raid event) contributes 35 'points' per skill level. So a trash SR with defender that you just picked up already starts at 35 points, or ~1/11th of the way to guarantee getting an SSR from 19 to 20.
Now take that random SR and feed it a single trash R weapon that you pulled from the gem gacha. Its skill is now lv 2, which means that it'd contribute 70 'points'. (R weapons contribute 10 times their skill level)
Then, to get that SR from lv 2 to lv 3, you need 20 points for 100% rate, which is two more R's. That'll get the SR to go from contributing 70 to contributing 105.
Or, just keep getting more unwanted SR weapons and toss them a random R to get them to lv 2.
Get 5 random SR weapons at skill level 2, then either 1 more SR weapon at skill level 1 or 3 more random R's to get to 380 points.

And that's not even taking into account grails. SR grails contribute 50 x level.

At the end of the day, whichever combination of SR weapons/grails you use to get to 380 points should take less than 10 weeks to acquire, AND it'll not cost a resource that could instead be used for the SR+ kamihime weapon or SSR ticket.
I prefer to avoid calling something outright bad as long as there are situations favourable to it, but this is one of those things for which there are no rational arguments in favour of.