Gangsters Forcibly Enter MMA Fighter’s Home — and the Decision Proves Deadly
There are lots of stories like that one, and a perusal of liveleak will corroborate this. Now, I'm jot saying that sport martial arts are the be all end all. I myself practice very non- sporting arts as well, one of them being for modern self-defence. However, all the scariest folks I know, some of which are self defense instructors and cops (or both), have a solid sporting MA background. After them, the scariest people I know are in my judo dojo. I'd be happy to have them at my back in a real fight.
Now, let's assume that your current training is adequately self-defence oriented and is of high quality. You likely don't need more of that. You need resistant training with high performing fighters. The best place to find them in most places is on a mat, or in a ring.
This is not new. Even in medieval Germany, wrestling was the primary unarmed art of the professional warrior class. These were people whose lives depended on their combat skills day to day, because they were out there fighting against people who were trying to kill them. One of the earliest manuals from the period states "all fencing comes from wrestling". By wrestling they meant grappling in general. So if the warriors of one of the most war torn places on earth said "wrestle", go do that. Furthermore, they were well aware of the benefits of sporting MA, as they did tournaments in peace time to keep themselves in fighting shape. I have more than enough data to support it... there's the whole martial history of Europe.
Now, maybe judo or wrestling aren't your cup of tea, and that's ok. Maybe the training won't resonate with you. That's ok too! However, I believe you'd be doing a great disservice to yourself by not trying.