This is probably too little, too late at this point but life in general has been hectic and when I had time to write something down, the website wasn’t cooperating. Anyway, here’s what you should know about weapon swapping.
First of all, it’s exactly what it sounds like: a rogue swaps weapons in the middle of a fight. Second, it looks like it benefits Assassination more than Combat.
The idea is to have two off-hand weapons. One has Deadly Poison while the other has either Instant or Wound, depending on your spec or what’s on the main hand. Once Deadly Poison stacks to five on your target, you switch to the off-hand that has the same poison as your main. The result is a DPS increase. For Assassination, that around 400-600. The benefits are lower for Combat. Hey, it has burst capabilities to make up for things so I wouldn’t worry about it.
Patch 3.3 is expected to drop within the next two weeks. It includes a change to Deadly Poison that will remove the need to swap weapons. Till then, give it a try. As long as you have nearly identical off-hands you should see a damage increase.