Yes, tokenVBL is powerful but with great power comes great responsibility
tokenVBL is meant for "Moveable" VBL. So that means every time you move a token, MapTool says, "go get me all the VBL" which is basically one object. But now when that is called, it now says, "and go get me a list of all the tokens that have tokenVBL and add that to the area".
1. IF you have either a lot of token VBL or a large 1 or 2, it's going to add CPU time.
2. If you use the AutoGenerate VBL it can grab a pretty accurate pixelated VBL. And that can add CPU as well.
So like the others said, your best bet is to transfer the final tokenVBL to the main VBL and that will help a lot. I do that for any statues or things that won't move as well. On average I have a dozen or so doors/items that end up being actual tokenVBL and performance is great.