WOW Gold: The melee sub jobs would make you more of a solo player in game
The demand for a FFXI Red Mage really increases significantly when you pass 40, that's the time when people want to cash WOW Gold in on your 'refresh' and 'convert abilities'.
At this level you may have much more say in the team than before, because early on the Mage has to play as a healer, a lot more than he might prefer, especially when you don't have a White Mage in the party.
Part-time Red Mages: A Red Mage/Black Mage combination will add to your MP and the black magic spells can always be useful, not to mention the elemental seal.
Another strong option is the White Mage sub job. Though this won't give you the sort of MP boost black magic gives, but still it would add a new dimension to your character making you more of a healer, when needed.
However, if you'd rather go for the melee option then forget about the Monk sub job. The Warrior can do better, with provoke and attack/defense boosts this would be a better option.
But really, the melee sub jobs would make you more of a solo player, because you can't work as a tank in a team and be a Mage.