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!
The first demon hunters, whether enthralled by the sight of Illidan Stormrage cutting down swaths of demons during the War of the Ancients, stumbling upon a rogue demon hunter in their eternal quest to slaughter the Burning Legion, somehow forcing themselves into the destroyed realm of Outland, or by secret scrolls that have been found in night elven lands, the Night Elf demon hunter has more avenues than Blood Elves to become the predator of demons. Most, if not all Player Character Night Elf demon hunters, are going to be shackled to the fact that they became demon hunters sometime after the War of the Ancients. This is ambiguous due to the information received in World of Warcraft: Legion by the character Illysanna Ravencrest in her Dungeon Journal entry, “The daughter of Lord Ravencrest, imprisoned for millennia in the Vault of the Wardens shortly after the War of Ancients, found herself free after Maiev released the demon hunters from their prison. Returning to her ancestral home, she has sacrificed everything - including her very soul - to defend what she could not during the War of the Ancients,” being taken by some people as evidence of her being a demon hunter either during the War of the Ancients.
Blizzard also announced a boxed Collector's Edition for World of Warcraft to ring in the game's 15th anniversary. It includes a Onyxia pin, map of Azeroth mouse pad, art prints, special anniversary mounts, and a large black-and-gold statue of Ragnaros the Firelord. It will release on October 8 for $100, and you can pre-purchase from the Blizzard store.
The main topic for Classic at the moment would be whether the game is actually harder or just has more redundant activities you have to do before doing the stuff that's really fun. This is actually a good discussion to have, and not just for WoW, but gaming in general. The main sticking point for now, as most people are on (relatively) low levels is the breaks between killing mobs, especially for mana users. In the beginning it's actually refreshing having to think about what you can and can't pull, not just running into a bunch of mobs and killing them in *insert current optimal time to kill Blizzard determined is the most fun*. The food/drink breaks after a few (or even one) mobs provide time to actually look around the scenery and the mobs you're facing, and while there isn't much strategy involved at these levels, you still at least pretend to plan out how you're going to get to that quest mob without being killed by the 4 random ones surrounding them. Not being able to pull whatever mob you want, and actually having to check what mobs are there when you don't have interrupts yet (casters tend to be a nightmare) is definitely more difficult in a real way than what we have today. As a caster, having to actually think about which spells to use based on mana cost (and perhaps even using lower ranked ones) is definitely more difficult and requires more engagement with your character than we have in modern WoW.