Hey there!
I’m not sure what happened back there. We ourselves are using StagTools on the last version of WordPress without any issues. I’d still make sure to give it a test on that.
StagTools generally makes use of shortcodes and widgets other than the additions in the editor and calls scripts/code only on pages it’s needed on. So it’s highly unlikely that it would affect the page load time, for me, after testing it with the Query Monitor plugins its barely 0.06 seconds with default installation.
On a second though it might be a conflict with current theme or any third-party plugin active. Can you give a try with twentyfourteen theme with no plugins active and see if you still get the load times issues?
