I like to solo or low-man stuff with a friend and melee rdm is very fun for that. Just be sure to have some gear sets! One for melee, one for black magic and one for white magic enfeebling spells.
Many buffs are only affected by your enhancing magic skill, so you can equip your melee set even when casing those spells. I like to keep -spell interruption gear on though, just in case.
With blink and stoneskin up, you can tank many enemies solo. Make sure they're at least decent challenges so you get skill ups.
As far as doing damage in a party setting, don't forget that you are able to magic burst with the black mage! It increases the accuracy so your C+ in elemental becomes way more efficient if you burst your nukes instead of spamming them.
Refresh is your best friend. Do everything you can to get it and also dispel at their corresponding levels.
GL