Thank you for your feedback and sorry for the late reply!
I am sorry to hear you experience performance issues. We consider performance our top priority.
The engine needs some time to update itself if you add/rename/remove file or reference, is that your case? As with any performance issues, it will be best if you could provide a JustTrace snapshot. Let me know if you need assistance with that.
As for the templates, does it happen with templates that use functions to be evaluated or it happens with any kind of template?
You could also open a support ticket and send us over the JustCode logs. You can find them in %localappdata%\JustCode\Logs
If you have any other problems or suggestions, please don't hesitate to write back!