would say I never run into the cap either.
Seeing as it'd Dungeon specific as well.

[Most of the Relics require to be at a certain stage anyways before you can grind it.]
<With Zeta, you need to get past books, and individual quest chains. you can save up the quest chains for the rest of the Relics at once. or the tome/gc items.
(so you'll decide to finish it before going onto the next one)
Anima doesn't have anything that will take forever to reach said cap, as you'll be required to reach a certain point that you may as well finish it, before going onto the next.>
we already know how the other Relics work, so any Dng stage wouldn't get you that far, even if you anti-towered.