I think the best all-around mage pet is pretty much always water, however, what pet you should use at any given time is pretty situational.
Water parses highest by a very small amount, and your pet is already a pretty small percentage of your overall damage on raids by that point so don't expect too much. For solo/group content I'd almost always go air for the stun, for raids go water, and for a small number of raid encounters where mechanics heavily favor ranged dps go fire. Could make an argument for going air against raid trash at times for the stun, but it's going to be inconsequential most of the time.
Redoing my web site so this may not stick, may not be valid, et cetera by the time you see it. I can't recall all the details, I think I just had pet damage going to window. Couple of fights, details as much as I can remember, Trixie was a level 62 Water Pet unfocused, Gibartik was a level 66 Air Pet or next level up. All buffs were the same, both with pet toys. After I ran this I got the impression the Air Pet was much better at damage mitigation so mostly kept the taunt on, but with two Magician Pets I could have just let them both go to town. Some of the goofyness in EQ is Pets can backstab from the front so positioning the Water Pet behind was probably unnecessary but I did it anyway. Of course nothing is straight forward, I mean I haven't checked if the Air Pet can stun from the front, if it was in some place like Sol B where everything is fire resistant, you would never use a Fire Pet, et cetera, et cetera. This was in The Bloodfields IIRC. pet-damage-spells.jpg (550×743) (rickcortese.com)
Each elemental pet has different resists during TLP eras. Sometimes the best dps pet is the one that survives ae damage. Water: vs poison (Trakanon) Earth: vs disease (Severilous) Air: vs cold (Gorenaire) Fire: vs fire (Talendor)
