Unequip your weapon then try to get the biggest Z combos you can, working in hits from skills as well.
Just unload Triple Geyser/Aero Tornado/Illusion Stinger on the miniboss and Treant. Spam Cannon Blade throughout the level with Raven. Aisha should have no problems with the skill combo part no matter what you do, but I strongly reccomend, as most would, that you get none of her 1st Job skills and wait until you get Hell Storm and Chain Burst, both which are multi-hit skills which work great for getting the skill rank up.
You should be able to S Rank time and hits taken regardless. Those two are generally pretty forgiving in general.