is there a limit you can do on dungeons?

[Barraind]

while it's possible to approach 10+ instances in an hour if you are doing something like light farming on a relic or anime, it's incredibly rare and something only done under very specific circumstances.

You can do about half of coil unsynced in a couple minutes.

Ifrit normal in 1-2 gcd's.

Moogle EX for crafting silly weapons is a minute or two.

Haukke for crafting stuff is pretty fast.