There are multiple tools and possibilities, and shure it would be nice to have something quick at hand. I know plugin authors who do offer debug flags so you can analyze what’s going on quite easy.
As for plugins, I have not tested it but looked at some screenshots and it is at least informative: Debug Bar (WordPress Plugin) and the BlackBox Debug Bar (WordPress Plugin).
Another one is a hooktracer that is not that well known: SJ Hook Profiler.
I do heavily recommend xdebug for development and testing systems, it’s a pleasure to have it if you need to profile or debug stuff.