There maybe some pets there is no reason to breed past level 1 depending on starting stats. But once the stats you can modify are max there is no real reason to breed anymore.
I had a baby that was created the morning before they removed the breeder for the most recent fix. when i was done leveling it to 30, i had over 800 points still availble to spend with nothing to spend them on.
In its current form, there really is no functionality for current bred pets, othan than fun. Donation pets are of course a better option (level 45, can adjust str/dex/int, and most have some stats far above 120), and good bio's are probably a better option now.
I agree Hit points are not everything, but I think being able to have the larger hit pools is what made the pre nerf pets viable, to make up for the deficiencies since they could not increase stats , or get skillls above 120 (powerscrolls) donations and bios can get skills 150+, higher str,dex,int etc.
Even with 2k hps i have never seen bred pets doing anything amazing. they were useful to a point, but useless agaisnt any tough mobs (especially some of the custom mobs). but maybe it was a problem, I dont know
The only thing i see now that might be considered "overpowered" are the same things that have been for along time. Prenerf icehound packs, werewolf packs (and i personally dont care what people are killing or doing with their pets)