Mend no longer seems to heal for 25% of the pet's hp, even if the tooltip shows the correct amount (indeed 25% of my pet's health) in its description. Despite the tooltip being accurate, I keep having pets only heal for about 20%. In an example case, I had my pet with 6340 hp use Mend and be healed for 1319. I don't have a screenshot handy, but it is a persistent case, so it shouldn't be hard to replicate this bug.

Did it take damage during the turn?

Was it above 75% Health?

Can you provide a screenshot of the Pet and Battle Log when this happens so I can see exactly what happened.

I am fairly certain that the pet in question didn't take damage during the turn, and it was not above 75% health, since the latter case would have explained it. You can't heal beyond 100%. I usually Mend at 75% or just below it, if possible. Regardless of whether damage was taken though, the combat log displays the actual healing that happens, separately from any damage taken in that turn.

I don't have a way of providing a screenshot at the moment, just going by what the combat log tells me, and what I have observed.

Do you use a Light Pet? Maybe it attacked first and proc'd a Heal?

The example was with a Fire specced pet. It went from 75% hp to 96% hp. Something I have commonly seen across many pets since the change. Previously it would always take them to 100% from 75%, with Mend, thus why I mention it. (And the anomaly in tooltip vs actual healing.)

Edit: No Light pets in the party, either. Not that you can proc a heal while using Mend...

If it happens again.

Just take a screenshot of the Pet and the Battle Log and whatever Health the pet was at prior.

I realized it's because Healing was changed to 75-100% like damage dealt.

The tooltip just wasn't updated.

I see... when/why was this change made?

When everything was implemented.

During testing, I felt it made more sense for healing to follow the same rules as dealing damage.