We have never used an affliction lock since we killed Illidan a couple of times. I always was the imp boy and did far less dmg than the destruction locks. A good thing about destruction warlocks is that they can use a curse without losing too much dps. An affliction warlock will lose a lot of dmg by using COS/E instead of COA. I do not believe that the extra 3% dmg done will be worth the loss of say 400+ dps from the aff lock speccing destro. Also note the ISB uptime you will have with another destro lock.
When i specced destro i went from about 1400 dps(this was half a year ago so can't remember excactly) maximum to aneasy 1800. And I can imagine the gap in dps becoming much bigger in sunwell gear where we get 2200-2500 dps steady on nuke fights.
Having 1 affliction lock is absolutely not a necessity. On fights where dps really matters, brutallus is the only one i can think of, we even have issues with debuffs getting pushed off without an aff lock. So imagine it being worse with even more dots on it.
Looking at your WWS I'm quite suprised at the dps chart. You 2 destro locks should be able to do a lot more dmg than the 900 average i saw. But that's kinda offpoint i guess. Looking at your gear 1400+ should be manageable with a decent group. Might be a group setup issue? And your hit is kinda low, more hit less haste
