Note: this is an issue that affected some pets in original WoW, but we don't yet know if it will apply to WoW Classic.
Almost all pets of the same level have the same base attributes. But some rare pets have inferior attributes. We don't know why, and we rather wish they didn't -- but they do. Because these pets have very high intelligence and spirit, we call them "caster" pets. Unfortunately, intelligence and spirit are not useful attributes for a pet. And all of the other attributes -- including health, armor, and DPS -- are lower for "casters" than for normal pets. So "casters" really are inferior creatures in all ways.
Before you tame the pet, the wild version of a "caster" will have a mana bar whereas normal pets do not. Note that some "casters" initially start with an empty mana bar but will drain your mana to fill theirs up.
After you tame the pet, you can check its attributes against those of a normal and those of known "casters" (below).
Of course, you can always skip all the fuss and just check Petopia before you go after a pet. "Casters" are prominently marked on all our pages in order to help you avoid them.
But how bad is it, really? There are some really gorgeous creatures that happen to have "caster" attributes. Can you make up for their faults with carefully-arranged abilities and talents? Or are they really just an utter loss?
"Casters" have between 80% and 83% of the base armor of a normal pet.
At level 10, this is a difference of less than 100 armor and can be easily made up with 5 TP in the Natural Armor passive ability.
Even at high levels, you can make up the difference with Natural Armor, but it's going to cost you a lot of Training Points.
"Casters" have about 95% of the base health of a normal pet at low levels, but this ramps down to only 80% of normal base health at high levels.
Missing out on 50 base health at level 20 is no big deal. Once again, you can easily make this up with 10 TP in the Great Stamina passive ability.
But at higher levels it's a lot harder to keep up. A level 43 Fire Roc needs an extra 343 health to match the base health of a normal level 43 pet. That would require Great Stamina (Rank 9), which costs 150 TP and isn't available until level 54 anyway.
We haven't worked out the exact differences in DPS. It is likely, however, that the base DPS of a "caster" pet is again only about 80% of normal base DPS at high levels.
To sum up, pets with "caster" attributes are fairly viable at low levels where the differences in their base attributes are relatively small. And you can help make up for their faults for a number of levels just by keeping up with the passive pet abilities Natural Armor and Great Stamina. But at higher levels, you'd have to spend all of your Training Points on these abilities and you'd still fall short. So if you really absolutely want that very special "caster" pet, you might give it a try -- but be ready for a challenge.