The changes slated for 5.2 will be, for the most part, a positive change and compromise between fun gameplay and intended gameplay. However, discussions on the WarcraftPets forums brings up some possible downsides.
The biggest one that I see is the "damage to the fleeing pet team" change. Taking into consideration the other changes coming in 5.2, will the damage penalty even be necessary? What is the purpose behind this change anyway?
Currently, the side effect of forfeiting a battle when the pet isn't ideal or desired is that it despawns the companion and its team. When players do this on especially hard to find pets (mainly in order to find a rare quality), like the Minfernal, Scourged Whelpling and so on, it's frustrating for others who would like to simply catch one, regardless of quality or breed. Since these particular pets are rare in the general sense of the word, despawning so many in such a short period of time is detrimental to others' gameplay.
But! With pets not despawning post-patch 5.2, this shouldn't be a problem anymore. Pets that are undesirable will instead be left alone OR manually killed off my players (in hopes to force one of different quality to spawn).
So how is the damage penalty for forfeiting a positive addition to Pet Battles?
On one hand, it does (negatively) reinforce the idea that to find certain pets, you must get your hands dirty and complete battle after battle before finding one. Simply plowing through pets and forfeiting probably isn't how this mini-game was designed to work.
But if you think about it, forfeit-hunting is still going to happen regardless if a damage penalty is in place. Forfeiting is easy, quick, and if I know anything about humans, it's that most generally like quick and easy. Not every practices this, but those that use it now probably won't change how they play the game due to a mechanic like damage after fleeing. If anything, they will find ways around it and continue doing what they've been doing.
At the moment, the damage penalty for fleeing a battle punishes those that may not even use the forfeit method to hunt for specific pets.
IF this damage penalty applies to Tamer battles, it will essentially be putting an annoying roadblock on the dailies. Many players, myself included, tend to forfeit a Tamer match in order to get a satisfactory line up. If my pet isn't strong or a good match up against the first opponent, I'll leave the battle and swap my current team around and then try again.
With this change in place, I'll have to bandage my team up after every swap out. Even if it's just a tiny bit of damage, who wants to start off an engagement without full life when you don't absolutely have to? It will be an irritating and unnecessary extra step.
Negative reinforcement to attempt to back players into a corner of desired/intended gameplay should be the last resort imo. If the goal is to encourage players to not forfeit, perhaps add some incentive rather than a punishment.
Maybe Battle-Stones have a higher drop-rate? Maybe players could earn some type of currency for successful battles that they could use to purchase unique pet items? Bonus experience? There are many options that positively reinforce rather than slapping players on the wrist.
If the goal of this change is to create an environment where all players will have a chance at hard to find pets, the new mechanic coming in 5.2 that doesn't despawn pets when a player forfeits helps this issue more so than a damage penalty. Players hunting for a specific quality, breed, color, etc. will be able to leave pets up for others (should they choose to) without having to go through any extra steps.
So in the end, what exactly does damage to the fleeing party "fix" or resolve? It's punishing to all Pet Battlers (regardless if they use the forfeit method or not), puts an unnecessary roadblock and irritant on Tamer battles (if this new mechanic applies to them, that is), and overall is more negative than positive.
Perhaps I have a knowledge gap, and if there's another reason for this specific change that I'm missing, I'd love to know.
And of course, much of this could change between now and 5.2 release. How the penalty is applied, how much damage, which battles, etc. could play a big factor in whether or not this change will help or hurt Pet Battles gameplay.