This may or may not apply to other Summoners, but I never used them before so I don't really know, and clearly the "balancing" of classes should be integral, following that line the balancing of skills of an OL should go hand-in.hand with the balancing of the pets' skill too:

Family skills (ie: Hibernation, Dark Field, etc) there are two for each family, why not make them random?, and we could re-roll with respect potions.

CoolDown time: Reduce time on skills, seriously, a mage pet has a lot of attacks but he CD is "insert -too damn high- meme", and not mentioning the Encouragement ones that takes 20 mins to cooldown.

Active skills: They do close to no damage, this needs to be revamped, ie: an unbuffed S3 Tank BD with all passives, self toggles, 186% cpow and 25K Patk does 119K critical damage with Cross of Valhalla to a Boss Scarecrow.

Armor skills: New ones: Vit, Vit/pdef for tanks; Cstspd, cstspd/eva for magic; Patck, Str/patck for melee.

Perception Attack: Too low, at lvl 15: Str/patk gives Str +95 and Patk +250; Int/Wis gives Int +155 and Wis +125; those are rookie numbers, make them % based of summoners.

Perception Defense: Same as attack, need to be % based of summoners.

Passives: Solid Body, Tome Analysis, Heel, etc, maybe could be % based as Penetrating eye, and add some others relevant to each type (mage, melee, tank, ranged, healer).

MIght of the Underworld: Make another one for mage OLs with Int/Vit; make it so the summoned pet takes the reduction so when you summon another one it won't change to that one or keeps bouncing between the two every 2-3 minutes, or make it so the second pet in formation takes de reduction.

Unique Unities: Allow the use of two unique pets with their unities on summoner without the constant bouncing between the unities of each one.