You are really looking at this the wrong way. The best self defense is having skills at all ranges of fighting. It is not an either or choice both have their place. Striking can be decisive in a way that grappling just can't match. A strike can take an oponent out in an instant. To forego that ability with the intention that you are only going to wrestle instead is assinine.
The Gracies have done good in their challenges. But if you watch the videos they do eat some shots getting their opponents down where they can work their Jiu Jitsu on them. There are people out there who you would not want to eat even one shot from and it's not always apparent just from looking at them. There is some validity to the Gracies being the cream of the crop in their art against opponents who were not equally skillful at their art.
But another factor to be considered is how their gameplan is going to work against multiple opponents, not a one on one honorable match. If you are on your feet you have mobility which you can use to keep your opponents from concentrating their efforts on you all at the same time. If you can keep moving while picking off opponents your odds are going to improve as you take people out.
It's not a rational plan to think you can grapple multiple opponents to the ground. You can take one down but you'll be tied up with him as his boys mob up on you. So you shouldn't plan on doing that. Now having said that I'll also say that if despite your best efforts you get taken down, if you can finish that guy off quick you might be able to get back up. So if you have the grappling skills it could save your ass.
I wouldn't say that anything is fool proof. But knees, eyes and throat are very effective. I've used and suffered through two out of the three and I have injured my knee before. They work and they can go a long way towards evening out a size and conditioning discrepency.