If there's anything I've learned from pre-opening coaster videos, it's to not judge a ride by it's speed. Everybody said Manta looked slow and it turned out to be just the right speed for all its elements; I can't imagine it going at a faster pace.
That said, while it does look a bit slower then I would even expect for a coaster of this size, I think the speed is going to be enhanced when you have the other side running too. I don't think you're going to notice the speed so much onride when you're watching the other coaster flyby and stuff. I expect you'll be paying more attention to that since it seems like these flybys are a little bit more drawn out then the really quick interactions on Dueling Dragons.