Not always. There are a few dungeons that have an overabundance of large monsters that cause issues with reliably hitting more than 2-3 at a time due to the size of their ring on the ground. Also some others where they are prone to spamming AOEs resulting in more time being spent avoiding damage than actually attacking.
As for the whole dps AoE too low or tank cooldowns being the only issue. There is another though it may just happen when tanking as a PLD where healers seem to think the PLD is supposed to handle healing so they can just stand in the middle of the mob and spam Holy which makes everything immune to stun after like 2 casts...