devs can u hear me

[Enkidoh]

Unfortunately as has been said, adding more tank and healing classes won't fix the issue, as it's simple pragmatism - tanking and healing in dungeons carries more responsibility, hence it's just easier for a lot of players to just use a DD class where they don't have to think and just hit stuff.

It's not a problem that has an easy fix, other than maybe find some friends and create a pre-made party that overrides the class requirement and enter a dungeon as all DDs? (Before you laugh, it is actually possible, albeit it would be more difficult, but it can be done - I main healed Toto-Rak as a SMN in a pre-made party for instance, but in that particular case we still had a proper tank).

There are always alternatives, but like much in life, they may require extra effort on your part to undertake.