Currently ATM I feel there are a few things that could fill out our current job roster.

Tank jobs that deal piercing or blunt damage. Could use 1handed pike + shield, 1h Warhammer + shield, 2h warmaul
A heavy melee DPS job to share medium armor with DRG. Maybe using a scythe, gunblade as either the 1h version or the 2 handed bastardbluss seen used by one of the bosses in HW.
Another melee DEX based DPS to share armor with NIN. Possibly adding another blunt damage user using a battle pole or tonfa
Melee range healer that utilizes both MP and TP. Maybe dancer like others have been asking for.
An actual Melee range mage. Everyone thought RDM would be this but its mostly a ranged caster that dives in sometimes for a melee combo.
A ranged physical DPS/support that doesn't use piercing damage.