Two packs (6 Mobs is what I aim for) a pull should be fine at ARR levels however in order of Level.
BRD, MCH, BLM, RDM: Level 18
SAM: Level26
MNK: Level26, 30
SMN: Level30 (Can multi dot prior)
DRG: Level 40
NIN: Level 42
Obviously check your comfort level. I've pulled dumb stuff in low level dungeons level capped. And don't worry about dying because you're testing your limits.
BRD, MCH, BLM, RDM: Level 18
SAM: Level26
MNK: Level26, 30
SMN: Level30 (Can multi dot prior)
DRG: Level 40
NIN: Level 42
Obviously check your comfort level. I've pulled dumb stuff in low level dungeons level capped. And don't worry about dying because you're testing your limits.