Korruptor that is correct. But I thought the OP was planning on having a team of 4 worgen/goblin + dk. Also one thing to consider is the new lowbie questing areas. Almost all the leveling guides I have read all say go to the bloodelf/dranei starting area regradless of your race. This is b/c the quest rewards are a lot better.

I don't know but I would think that the goblin/worgen areas would be the next best place to level your toons.

So In the situation you laid out

upgraded to Cat account a : Make Goblin/Worgen
upgraded to Cat account b: Make Goblin/Worgen
Vanilla wow RAFed to account a: make human/orc
Vanilla wow RAFed to account b: make human/orc

You could do this but to get the full team you are going to have to do it twice before you get 4 goblin/worgen.