Always keep in mind that if your overall attack is over 33-35k any further increase in raw numbers won't be as significant as an increase in Assault Skill Levels, I guess Overall Attack is just to show off your experience in the game and how many events you've been in but in the end a 33k High Skill Level / Mono Weapon Grid beats a 43k Rainbow Weapon Grid by far.

So if 10k Overall attack doesn't even match high Skill Levels in a Mono Grid then why would you bother rushing on +99'ing your weapon/eidolon?

Seems like a dumb move to me, you're meant to get those ocasionally whilst you Skill Level Up your weapons, in my opinion.