Ed and Single Six,
You both make very good points. Training to do things the same way, or assuming that an opponent will always present in a certain way, is a dangerous fallacy.
At beginner stages, when basic skills are being developed, there is a need to limit the way in which the aggressor presents - if the initial steps are too challenging, many folks just quit. Once basic skills are in place, scenarios should become more and more fluid as the student progresses.
Against a properly trained shooter, by which I mean one who has actually trained for up-close encounters and who is aware not only in thought but also in body movement, my chances of success drop significantly. They don't cease to exist, but they are much lower than they would be against a shooter who only practices at a range, shooting slow fire in controlled conditions.
The way I normally train at any given technique set, because this is how I was trained when I began, goes something like this:
1) Start from static, with aggressor grabbing; apply technique (this is hard in its own way - my style, aikido, uses redirection of force more than it uses force creation, and a static aggressor doesn't impart much force to be redirected).
2) Have aggressor grab, and apply technique as he is in motion.
3a) Have aggressor throw straight punch, and apply technique as he is in motion.
3b) Have aggressor throw hook or roundhouse punch, and apply technique as he is in motion.
4a and b) Same as 3, but with kick instead of punch.
5a and b) Same as 3, but with weapon (training knife, sword, or staff) instead of punch.
6) Multiple attacker drills, using same type of progressions as 1-5.
Obviously, somebody who is comfortable at the tougher end of 6 is a very different practitioner than one who is only comfortable at 1 or 2.
Also, while progressing through 1-6, at each step of the process, speeds should go from slow to faster. Most people try to start too fast. Going slowly actually is better for revealing points at which one has put oneself off balance, or is applying too much muscle.
(In aikido, position and balance are what make things work; application of raw force often causes techniques not to work.)
A couple things I find interesting:
first, that good techniques will actually work against the full range, from static grabs to multiple attackers; although the techniques will have to be adapted slightly, their basic mechanics don't really change;
and second, that position and distance generally matter more at any given point and in any given technique than what the hands are doing.
Beginners tend to fixate on their hands; advanced students get to superior positions, while keeping their own balance and taking away their opponent's balance.
My first goal is to not take a direct hit; my second goal is to achieve a position where I have multiple attack options open, but the opponent has very limited options.
Example, on rear flank of opponent, with my hips oriented toward him, and his hips oriented back where I used to be. He has to come around the long way, whereas I can hit or kick from either side, employ a weapon, bite the guy, etc.
Closer is generally better than farther away. A couple feet away from him, I have given him room to launch a kick, or to turn back toward me. Right up against him, I have him naturally jammed. He can't throw the kick; if he lifts a foot, our relative positions force him off balance. If he tries to throw an elbow or back-fist, my relaxed, unflexed arm is already in the way as a shock absorber. When he tries to move, I just stick to him and take him down.
Again, the opponent's training and skill set matter, too, but you'd be surprised how many people have trained for boxing / kickboxing / TKD type scenarios, where hits and kicks have to be to the front, and where fighters maintain some distance; yet those people often have no idea what to do with somebody who deliberately avoids being in front.
Movement matters. A lot.
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