Hi,
I'm actually going to come at this from another angle.... essentially, I'm going to state that no martial arts are designed for self defence. And the real meaning is not self defence, or even combat effectiveness. That is simply the vehicle used to get to what they are really all about.
Okay, a little different I'll admit, martial arts aren't about fighting and all that, but I'll explain.
To begin with, let's look at them objectively. Martial arts, as we often say, take at least a lifetime to master. It is an ever-constant journey towards the refinement of mind, body, spirit, and more. Self defence, or combat effectiveness, on the other hand, requires short term training. There's no point taking a potential soldier, and teaching them for 4 decades until you consider that they have "mastered" the combat enough to be sent out on duty. By the same token, someone who needs self defence capabilities needs them now, not 15 years down the track. So, to be completely honest about it, martial arts are not really the best approach for self defence.
As a case study, we'll look at a very highly respected martial art, the Tenshin Shoden Katori Shinto Ryu, as well as more modern systems, such as Aikido.
The Katori Shinto Ryu was said to be founded in 1447 by Iizasa Choisai Ienao, who, after a long, distinguished career as a soldier (using spear and other long-arms on the battlefield), came to the Katori Shrine. One of his men allowed Iizasa's horse to be washed in a sacred shrine. The horse actually then died, which Iizasa took as a good sign, showing the power of the Deity of the Katori Shrine, known as Futsunushi no Mikoto, a warrior deity. Iizasa then spent the next 1000 days training and praying at the shrine, at the end of which he had a dream in which the Deity of the shrine appeared to him, telling him he would be the teacher of the future of Japan's Shoguns, and handing him a scroll called Mokuroku Heiho no Shinsho. When he awoke, he had the scroll in his hands. As a result, he named the new art Tenshin Shoden Katori Shinto Ryu (The correctly transmitted from Heaven martial arts and spiritual traditions of the Katori Deity - loosely translated).
The teachings of this Ryu begin with the words "heiho wa heiho nari", meaning "the ways of war (heiho - soldier methods) are the ways of peace (heiho - written with different characters)", showing that the Ryu holds the belief that peace is preferable, and therefore the combative techniques are to be trained so you can avoid violence. Add to that the rules you must abide by when you join the Ryu include the dictate that you are not allowed to cross swords with members of other systems until you have achieved complete mastery in the Katori Shinto Ryu (in other words, if you are a member of the Katori Shinto Ryu, a highly respected system which has produced some of the finest swordsmen in Japan's history, then you are forbidden to engage in fighting, or even friendly competition with anyone else). This, to me at least, doesn't seem like the structure for a system primarily concerned with self defence or combative effectiveness.
So that's the philosophy. But how about the techniques? The Katori Shinto Ryu has a large curriculum, involving a range of weapons, but focusing on the use of sword. Now, at the time of Iizasa, the sword was not a primary battlefield weapon (it never was, really), instead, naginata, yari, and yumi were (Japanese halberd, spear, bow and arrow). The sword would, at best, be a secondary weapon that you would fall back to if you lost your main one. However, the sword is incredibly good for teaching strategy, angles, targeting, distance, spirit, and more, and by being skilled with the sword, the art then teaches you how to use it against other weapons. However, it really should be noted that these weapons and techniques are taught not for combative effectiveness (although they certainly are highly effective), but for the other benefits that the training brings. After all, being focused on swordwork at a time when sword was least likely to be used is not the hallmark of a systems based on combative use.
When we look at more modern systems such as Aikido, Karate, Tae Kwon Do, and pretty much all others that get labelled as martial arts, we find similar things. They are teaching techniques that, frankly, are not designed for the style of assaults that aer encountered today, as well as often teaching responces that are inappropriate, overkill, or in a number of cases, unrealistic. However, that denies why they are there in the first place. Just like the Katori Shinto Ryu teaching sword when it is not of primary use, teh techniques of many martial arts are designed to teach a number of other skills/tactics/strategies and so on, rather than the more commonly thought "answer A to attack 23" type of structure.
Aikido's attacking rhythms, for example, are unarmed representations of sword attacks. Are you likely to be attacked that way? No. Does it allow Aikido to teach their philosophies and strategies in a highly effective way? Yes. And for an art, that is far more important than being immediately applicable for self defence.
So where did this idea of martial arts being good for self defence come from? Well, we've been exposed to a large number of images from movies, TV shows, comics, and more. We get bombarded by advertisements from martial art schools who all claim that they are teaching "effective self defence", so we naturally believe it. After all, every source of information around us tells us that all martial arts are good for self defence. Unfortunately, no martial arts are. They are simply not designed to be.
So what should you do if you want self defence? Well, that's where RBSD systems come in. They are not concerned with breadth of knowledge, philosophies, skill sets, or anything that gives a martial art it's depth. Instead, they are concerned almost exclusively with drilling you to be able to handle a modern assault. They are best coupled with Defensive Tactics Programs (DefTacs), which give a small technical base, again without the depth of a full system. But to be good at them, they need to be trained hard, and feature a huge amount of repetition. Unfortunately, as there is very little to the system in the first place, it doesn't lend itself to long-term study.
When it comes to sport systems, the sporting (competitive) side of things is just another way to approach the arts. Realistically, it is kind of halfway between the two methods (the "pure" martial art, and the DefTac approach). It will give greater longevity than a DefTac approach, but not as long as a more traditional martial system.
I guess in the end, it comes down to what are you wanting out of your study. If it's purely self defence and combat effectiveness, to be blunt, martial arts are not the best. But that is a rarity, that it is needed immediately, and martial arts can certainly give you all the skills you need for self defence. It should just be recognised that that is not what they are for. And that is not very well recognised these days.
) 
JMO 
