Dual-stat specialists don't work for leveling items, you have to use the regular/single stat ones if you want to get the best of that particular stat. Also, I believe you're referring to Mediators for creating dual-stat innocents (Mentors are used to get skill levels faster). They are not worth the time farming either, you don't really need them for anything, so your time is better spent on perfecting your items (or at least as much as you can bother with it)

引用自 neemoos：

Dual-stat specialists don't work for leveling items, you have to use the regular/single stat ones if you want to get the best of that particular stat. Also, I believe you're referring to Mediators for creating dual-stat innocents (Mentors are used to get skill levels faster). They are not worth the time farming either, you don't really need them for anything, so your time is better spent on perfecting your items (or at least as much as you can bother with it)

Then i wonder whats the point of duel-stat innocents... do they have a use at all?

The point is just the flat bonus they provide for less space and that's it. Like, once you've maxed out your characters and have them with perfected items and such, filling the slots with dual-stat specialists would be better than the single ones. It's just that there's nothing that warrants their use for the time it takes to get them to a decent level.

In later entries it might be a different story - I don't remember when it was introduced, but in some Disgaea games you can dupe items (and the innocents within), making the effort of farming AND maxing them out almost non-existant.