I've wondered the same thing about a Mini 14 Ranch. Quoting from the web site -
"With the new thicker tapered barrel, we've seen up to 33% reduction, but sometimes it is much less, or there is no noticeable improvement at all. As always, YMMV."
Sounds like this would apply to both the Mini 14 and Mini 30. My guess is it will depend a lot on the group size your rifle shoots before installing the Accu-Strut. If it's capable of an inch or two at 100 yds, you're probably not going to see much improvement. If you can't do better than a 5 or 6 inch group and are getting flyers that aren't shooter-caused, It's probably worth a try.
I'm planning on buying an Accu-strut and a Mo-Reaper when I get my Mini 14 back from Ruger, but to be honest it's partly (maybe even largely) because I like the look. If I can get a little improvement in accuracy too, I'll be happy.