For the swimm part I just have to say I hated all the Quests in WoW where you had to kill some guys underwater. It was so annoying and i had a lot of problem with targeting the enemies.
also there was a quest where you had to kill some dead marines on boats and this quests was so buggy that i was killed multiple times just because i wasn't able to target something or the target could hit me but it said I had no Line of Sight...
I'm really happy they left the swimming out
and for the Jumping, I was unhappy too at the beginning but after a while you don't notice it anymore, you just get used to it.... But in the beginning (especially if you were playing WoW before) you really miss it.
And i really think the code would be much more complex if they would add it to the game and besides what would be the diffrence in the game especially in pvp?