I have had an issue with Black Mage MP even as a Taru since the level cap increase. I feel that even with convert and conserve MP, that the issues I have are related more to the new MP costs of our new tier of nukes, Tier 5.
Ever since the release of the new tier nukes, our MP pool hasn't gone up much at all to compensate the new MP costs for the tier 5 nukes and also the damage output of the tier 5 Nukes aren't worth it if you are outside of abyssea because I found the tier 4 nukes to be more efficient for Damage per MP cost, but in Abyssea I have no problem casting the Tier 5 nukes because I have almost a double sized MP pool AND high mp refresh. A higher MP pool allows convert to be more efficient and allows a higher chance at getting a conserve MP to proc without running out of MP in 3 blizzard 5's.
So all that being said, if you ask me BLM need something more than just a simple auto refresh. I think they should take a look at the MP costs of each nuke and lower tier 5 only or lower all nukes by a total %, to keep them scaling the same.