Monster Rearing Charm Confusion

So I've been interested in doing Monster Rearing, because I tried to unlock every possible Capacity Bonus thing. I've only got the Rank 1 monsters for now, so I chose Red Foliage Treant, since I am a GEO, plus I want to become a WHM too, so it seemed like a great idea.

I just now did the Cheer quest, and compared things by using Geo-Barrier, a defense increasing spell. Perhaps that was a dumb idea, since as I now discover, the increase in DEF does seem to depend on your current DEF, but regardless, I gave it a try, both with low Geomancy and Handbell skill, and another test with all the equipment boosting those things, capping it at over 900, plus tests with Blaze of Glory as well, and... all the results were lesser than before!

I tried doing the calculations with the percent increase of DEF, and where the results made more sense, but it felt like the cheer does hardly any difference, sometimes more, sometimes less.

This makes me wonder how these cheers work at all, and I was wondering if anybody here could provide me with some insight.

Thank you very much!

They generally are pretty low but you're talking about a rank 1 cheer which will generally be the weakest.

Overall cheers will either benefit you in the form of a EXP or CP increase or your trusts, some of the trust boosts are quite useful.

Then there's the 3% movement speed cheer that stacks with gear movement speed.

Ok so Red Treant gives these as Cheers.
Healing Magic Skill Gain +10%
Enhancing Magic Skill Gain +10%
Geomancy Skill Gain +10%
Handbell Skill Gain +10%
Alter Ego Magic Defense Bonus +5

No wheres does that help with Physical Defense so "Barrier" won't change at all from it.

Now maybe you confused this "Alter Ego Magic Defense Bonus +5"
A) Its for Trusts only not you or any other Player Character.
B) Its Magic Defense Bonus which you can't see how much you have in game but is "Fend" for a Geo.

Edit:
Maybe you misunderstood Skill Gain too. Skill Gain from cheers helps you gain levels of skill faster. In this case you would skill up faster in Healing, Enhancing, Geo & Handbell if they're not capped skill for you already.

Skill gain rate?! But it...
*looks up again*
Oh boy, I so easily manage to misunderstand everything...

I did not realize it was just for Skill gain rate! I was certain it strengthened your magic or something... how embarrassing...

I do still have to cap my healing magic, so it's not a complete waste at least.

Just to know, can there always only be one active Cheer and do they truly "level up"?

You can only have 1 cheer active, they don't rank up but there are different tiers of pets so for example Rabbit Cheer is rank 1 while Lunar Wyrm cheer is rank 7.

BG page is VERY useful for monster rearing.

https://www.bg-wiki.com/bg/Category:Mog_Garden#Monster_Rearing