There are 2 downside of BLM strat compare with melee strat though:
1) It's completely useless against NM with high magic evasion or magic shield. One of the T4 is aren't killed with BLM strat, there's a couple more lower tier NM that's more ideal to use physical dmg as well.
2) It has lower "DPS ceiling" than melees. Like I said melee has higher DPS ceiling when they are capped haste spamming WS that SC with each other.
BLU v.s other melee is more of an issue because BLU v.s other melee has way more upside than downside(defensively, at least), thus preventing other melee gets invite to party. BLM doesn't prevent any job gets party invite. Anytime the content is more ideal to use mage setup, BLM the only choice and there's nothing else to choose from, anytime the content is more ideal to use melee setup it'll never get picked.