This is the second site on which I've tried Hummingbird, both with mixed results but I appreciate it's early days.
Turning on minification with the default settings causes this site to look very strange (I know this is not unusual). Sometimes it appeared to be loading in Mac Chrome as a mobile site, but parts of the page did not load. I think combination/minification breaks visual composer. Given its prevalence, some settings or guidance would be a good thing for widespread Hummingbird acceptance.
I selectively turned things off until none of the files were minified or combined. Every file had include "on", minify and combine was "off" and they were all in their original location. Unfortunately, with these settings the Nivo image slider that is part of the theme presented a black box with a neverending loading symbol.
This was the best I could get, but it's a live site and I can't leave it like that. I had to turn off minification entirely. However, I was able to get it to this state with about half the files included in minify and/or combine. If we can fix the slider, it could be worth using.
While testing, I turned off Cloudflare and WP Super Cache, but I will turn them on after I send this. Support access is on if you need to have a look. I didn't create the site, I just maintain it. From what I've seen, it's a bit hacked together. There are changes directly to the Story theme without a child theme and other odd things in there.