We have 2 white mages, 2 paladins and 2 bards in our coil grp + a black mage and monk, so... we'll never ever use more than lv 1 limit ever again because we just happen to have chosen to play those specs and play together. It's not that I don't get the intention (you want all classes to be equally wanted) but that's just not gonna happen, here's why:

1. Guys like us - we have our main jobs and we'll stick with them, nobody is gonna trash his/her almost full raidgeared toon to reroll a less liked class so we can fill limit faster - bascially you're hurting people for no reason.

2. Random groups in need of tanks and healers will take what's available - should that not be diverse it smply won't matter, 2 bards for ADS for example will still be wanted by many because it is the easiest setup to play - basically punishing people for not wanting o wait around until you have 8 able guys with different jobs in grp.

If you don't want people to stack one or the other dps simply adjust your weird rule to "starting from 3 of the same class blabla" but the way it is now it's just dumb and hurting all kinds of people.