Here's my idea for a possible class. I know that it doesn't have much basis in Warcraft lore but they could always add in more stuff and I think it would be a good addition to the gameplay.
Summoner This is basically similar to the Summoner job in the Final Fantasy series.
1. Basically on their own would be like a weaker version of a priest but with "familiars," which serve as weak pets, like a Hunter Pet or Demon but less powerful. Familiars stay by a Summoner's side at all times and a Summoner can only have one out at a time. These Familiars can be commanded to an extent just like a regular pet, and a Summoner can choose what abilities they use outside of battle but in battle they cannot directly command Familiars to use specific abilities.
2. This is where the Summons come in. I'll just call them Eidolons for now since I can't think of a better term atm. Eidolons are much more powerful than Familiars and as such are only summoned for a limited amount of time and when they're out a Familiar can't be out at the same time. They have loads of HP and a Summoner can can directly command them to use specific powers.
3. A possible way to tie this in with the lore is that Warlocks are magic users who derive their powers from evil, summoned creatures. Summoners are not evil and take this a step further. There are already Familiars that exist in lore and gameplay. Plus there are already creatures which can be called forth temporarily (a Scarlet Mage calling a Phoenix, and Summon Water Elemental), so why not this? Also it's a fairly common aspect of gameplay for an NPC to give you an item that lets you call on reinforcements.
4. Possible talent specs could be choosing to focus on Familiars, Eidolons, or personal non-pet abilities. Further specializations could be what creatures a person decides to make Familiars out of (just like Hunters with animals).
5. Plays can have a greater individualization by choosing between a variety of ptential Familiars. A Summoner can use Beasts, Elementals, Demons or Undead.