If they need to do things for "balance", then we do need more tanks and healers for a different kind of balance: the total number of classes available.

Currently we have (at best) three tanks, three healers and eight DPS classes - or two healers and nine DPS if people want to level summoner rather than scholar.

The average dungeon queue is made up of people leveling their various classes.

Dungeons need a ratio of 1:1:2 for the classes, and yet the actual ratio of classes is not in line with that. (Even before factoring in that tanks level faster than DPS classes due to near-constant EXP bonuses for being in need.)

So....

Ideal ratio: (and number variants)
1:1:2
3:3:6
4:4:8
Let's say that the number of DPS should be equal to the number of tanks + healers.

What we have:
3:3:8 --- (33% over ideal number of DPS)
3:2:9 --- (80% over ideal number)


With one extra of each role added:
4:4:9 (12.5% over ideal)
4:3:10 (43% over ideal)

So if I've done my maths right (I am very tired though) that seems like it should make quite a difference to the ratio of how many DPS to other classes there are.