Mormo doesn't look all that challenging, considering the area's wide space and his very diminutive size, and his movepool.
Then again, he was practically useless in battle in the first Radiant Mythology anyway (considering how all he did was be your mouth to boot).. How many useless Tales characters battle wise were there again? In Phantasia, I always had the healer and mage (Mint and Klarth) sit and the back and cast magic, while the fighter (Cless) and bowman (Chester) are in front row. In cases where Arche is required, I'd have her lay back with the other spellcasters.
This may not be the case for the rest of the Tales games probably after Destiny.. Idunno.