You don't need to use shadow partner.
You are putting off your best skill combo, that's like me putting off Ice strike for thunder spear. Thunder spear is powerful but its extremely slow and is no where near the ability of Ice strike, to even use it efficiently you need Spell Booster.
In theory with three mesos your meso explosion hits enough % damage to add up to 810% damage.
I really can't stress enough that meso explosion is
THE BEST 3RD JOB SKILL IN THE GAME!
>go to FM
>find store selling rocks
>buy 3 stacks
and you're done.
And Pickpocket pays for that!
EDIT: For the record I don't think any other class even has a skill that hits 810% damage on one monster, and can be done on up to 10 monsters.
EDIT2: well after Jump Glacial chain does more then that on 12 guys, but that's a fourth job skill, and in your fourth job you get a skill that adds even more damage to meso explosion.