I can hit a sheet of paper about 80% of the time with my G19 from 50yds while standing. It took me several thousand rounds and more than 5 years of practice to achieve this. I don't know what your measure of a "decent" group is, but if someone is having difficulty hitting a sheet of paper at "defensive distances" while at the range, I don't want them anywhere near me while they are carrying.
...just my braggy $.02