Is this game an iOS/Android app, or a desktop app? And especially if it's for mobile, which Render Mode are you using? Since you mentioned that you're not using Starling, I'm guessing you're using mostly vector graphics, and you may want to try setting render mode to GPU in your application xml if you're not already to see how that affects performance (at least for mobile, I don't believe this has any effect on desktop). A lot of our mobile apps use vector graphics as well for characters, clothing, and other assets, and using GPU render mode rather than CPU can make a big difference if you're using the classic display list.
Aside from that, there could be a number of things making the game laggy -- too much vector information on screen at once, heavy use of masking, heavy use of alpha transparency, etc. Especially if you're not using Starling, you'll likely want to spend a chunk of time optimizing all of your vector art, and seeing if there are any static elements you can render into BitmapData to improve performance, etc.