For me DNC's mobility lies mostly with En Avant. Having three charges of an on demand forward dash is so freeing that it makes it hard to switch to other ranged classes after using it.

SMN may have a good amount of instant spells but the lack of any movement abilities (besides Ifrit's one charge per cycle) means it's not even CLOSE to the mobility of those classes.

As a DNC being caught in a bad position during a mechanic is often just a single dash to safety all while maintaining constant dps.

SMN gets caught out you either sprint if it's up and hope, or sit there and hope your tiny self shield can eat it and take the vuln stack.