Yep. If I recall correctly, Lion/Tiger hybrids are also fertile.

The "produces offspring that can't breed" description is, I believe, used as a "simplified" explanation of what a species is. It's meant to prevent unnecessary confusion for presumably non-biologist audiences. (Such as what you'd run into in a high school biology course.) It's certainly not the only topic where a simpler, technically incorrect, answer is given in a school environment.

I also have a hard time believing the orc/draenei breeding. It would be one thing if both species were from the same planet, at least then you could speculate that they have some similar ancestory that makes them genetically compatible, but Draenei are from Argus. They fled to Draenor when the Burning Legion took over their home world.

But, this is Blizzard's world. They have ogres breeding with orcs, Keepers of the Grove breeding with Earth Elementals, and a Moon Goddess of unknown form getting jiggy with a giant stag. Part of the game is a suspension of disbelief, to accept what it tells us is possible in this world, even if it's not possible in ours. And for that reason, I can accept the existence of hybrids.