Climbing & Swimming

[kyuven]

I feel like EVERY other MMORPG out there has it

While some games do something with it, I really have to point out that MMOs with swimming mechanics fall into 3 different categories:
1) It's just like fighting on the ground, except with a breath meter and 3 dimensional movement. Boring.
2) It's a completely different experience (very few MMOs do this since it requires basically building two completely different combat systems.
3) Similar to #1, but has more physics in play than just the breath meter. The most infamous example is probably the original EverQuest. While underwater, you were subject to 3D movement but with "ice" slide mechanics, so if you got hit it was an automatic interrupt.

The key thing here is the games that had it, had it since the beginning. There's a lot of work and testing that goes into to to ensure you don't have people swimming above the water. The amount of work required basically ensures that, if it's not there at launch, it'll never be there.

Climbing on the other hand is a lot easier (comparatively) to implement, but don't expect it any time soon.