Louelle is an earth element magic damage dealer that can cast pretty fast. She has high MAG and 3 different offensive mage jobs that can make her effective in certain situations. Scholar sub job can be potentially deadly against bosses or pvp, Rune Knight makes her a strong Lightning element killer, while Black Mage sub job comes with non elemental spells that can be used on most enemies.
Her Rune Knight sub job comes with more non-casting damage abilities, but at a shorter range. Stonega Blade deals high damage, and is effective against Lightning enemies. Black Mage sub job are all low AP damage spells with no side effects. Some of them are elementless, which can be good if you want to use her against Wind enemies.
Her EX upgrade can potentially be a game changer, at least until 22. Job level 19 increases the ATK value of Earthen Calling and makes it into a non casting ability. At 22, Magic Orb becomes an instant ability that can reduce enemy's AP.
The TMR is kinda restricted to certain job tho, and as Agrias user I think you should be more worried about confusion as her LB has a long attack. Remember that Candescent Hew has 67% change of confusion, while Judgment Blade only has 25 % change of stop.
That houseglass figure making me sapiosexual but who is coming up with these names