Since MANY of us are bemused about the relative balance of pets, I have an idea that could use ALOT of input.

Basic premise: Pets of like taming difficulty and control slots should have like abilities, like damage output, like stats, like HP, like skills and like resists.

For best balance results, we could/would use the best creature of each control slot category / taming difficulty. Rideable counts as an ability. Skills not normally belonging to pets is an ability. As is magic, firebreath, special moves, pack attack, etc.
For resists, skills and stats, we would use as a bench mark the MAX and MIN (vetmaster as source) TOTAL stats, skills and resists for post tame of the best creature in each taming category. This way, they can be divided among the categories to better suit the design view of the pet.

Things I am not sure about. Should skills over 100 be counted as an ability, part of the skill total, or both? Should skills over 120 count as 1 or 2 abilities, part of the skill total, or both? (since 120 is max skill that we are used to.). Does the ability to gain over 100 skill count as an ability ( reptalon, hiryu can). Is flying REALLY an ability? It causes more difficulty than advantage. I count it as a disability really.

First, we would construct a table showing current balance. Then make a new table showing our suggestions.

You will be SURPRISED at how unbalanced the Rune Beetle is compared to other 3 slot pets of same taming difficulty (93.1!!!!!!), especially if you count each skill over 100 as an ability. By comparison, mare, uni, ki-rin are 95.1.
Rune beetle breakdown:
poisoning skill over 140 (+2), mage/eval/med/resists skill(+4), poisoning (+1), bleed (+1), magery ability (+1), corrode (+1), partial poison immune (+1/2). Total ability of 10!!! This is the most of any creature.)
Total abilities 10 1/2

Total resists 320

Total stats 580

Max HP 360.

damage range

By comparison, the old favorite, the WW (taming 96.3) has:
Total abilities 1

Total resists 280

Total stats 1,315

Max HP 456

table would look something like
Title: Two Slot Pets
Taming range / # Total Abilities / # Total Max Stats / # Min stats / Total max resists/ Total min resists / Total max skills /Total min skills / Damage range / Max HP / Min HP.

I will have to re-read this tomorrow when I can see straight

First, I wouldnt count any skill over 100 as an ability. Just toss it into the skill total. Also, for the skill total, Id use maximums and values after training. Pretty sure that after taming the Rune Beelte can only retain less than 120 Poisoning anyway.

So Rune Beetle would have Bleed, Armor Corrosion, Poisoning, and partial poison immunity as "abilities."

I like that table you have laid out. Might need a bit of tweaking to give the pets more of a single number rating system bassed on everything you have laid out there...like Kits calculator.

Maybe even just bold the highest values for a given column per control slot?

Im with Kit, Il be seeing straighter tomorrow and will reread it