When hovering over an ability, the tooltip will tell you whether or not that attack is weak or strong against certain pet types. Additionally, you can hover over the opposing team's pets and view their attacks during combat. This will be important since it’s a good idea to pit a pet that's strong against the opponent's pet who's vulnerable to that type.
One player said in a comment posted in response to the list, “Yeah people don’t realize the sheer enormity of game system evolution WoW has gone through since release. I’m not the biggest fan of BoA by any stretch, but I’ve played since closed beta vanilla, and I doubt I’ll be going back to classic. Leveling was painful. Experiencing these old systems once was enough.”
I consider myself a purist in that I would prefer classic to be released as close as possible to the original. Where that is on the spectrum of patch content will be up to blizz. I'm also not vane enough to believe that any single state of the game is the "Ideal" location we should be aiming for. There is common ground that we can agree on, and I would welcome more than a few changes as long as they are made in the spirit of keeping classic on the vanilla rails.
Each battle that you win will yield experience for each pet that participated. However, deceased companions will not receive any experience (so make an effort to keep them alive by swaping in a different pet). Experience gains are based on your pet's level compared to the wild pet. Defeating a higher level opponent will grant more experience than a much lower level one, but be ready for a tough fight!