What makes a unit elite? The kind that might stand up to 100 soldiers, the type that inspire songs, the kind of "Names that are worth 1000 swords" (Gandalf, LotR3). Consider these two anecdotes about experience and diminishing returns:

First, a short ancedote, more of a metaphore about how diminishing returns might apply to any field: My lawn is pretty nice. It's nicer than my neighbor's lawn -- but not that much nicer. I'd say my lawn is about 50% nicer than my neighbor's lawn, and he doesn't do a damn thing; occasionally, he'll let a boy from the neighborhood mow it and water it, but basically, he doesn't really do much else. I, on the other hand, weed, mow, fertilize, water like crazy, all at the right times. I'd say I put in about 400% more effort into my lawn than he does. This shows, but not to 400%; my lawn is about 50% nicer. I could work double as hard on it, but I think my lawn would then only look about 65% better as his for 800% of the effort. Yet, by hiring specialists in this special type of urban grass, perhaps an exterior landscaper, and what not, investing instead of $100 a year on water and fertilizer, by investing $500 or so, I might get the lawn to look about 150% better -- that would be a true breakthrough. But even here, there would be limits. At one point, even having a private, personal gardener at my beck and call day in and day out will not really improve my lawn any more. Admittedly, this is a poor and unexciting example, yet I think it demonstrates that in some aspects of gameplay, the diminishing returns are stronger than others, and the breakthroughs might come earlier, or in much more segmented or abrupt levels.

Now, combat. I have been engaged in martial arts of one sort or another for about 25 years. Currently, I engage in MMA (mixed martial arts) at a sub-competetive level; kickboxing, jiu-jitsu, and judo are my secondary sub-disciplines, which I have practiced for about 2 years each, I perform at a sub-competetive level, with wrestling as my primary fighting style, which I have been doing for about 15 years, I perform as a sub-discipline at a competetive level. In my weight class in wrestling, I am fairly decent. In unarmed combat against a single untrained opponent, I am fairly confident that something very bizarre would have to happen for me to lose, no matter what that person's weight class. (I weigh 68kg, and have fought against real monster bodybuilders of 130kg who are only mediocre boxers without too much of a problem.) In other words, I believe that I am in a very high percentile bracket of the world's population; I think with my training that I could defeat 98% of the population of humans age 16 and up. Yet to do this, I had to stop training wrestling and start learning strikes (kickboxing), chokes, and joint manipulation (BJJ and traditional jiu-jitsu); with 15 years of wrestling, I was not fit for combat, although in grappling situations (but those only) I would have a huge advantage over many people. With only 1 year of kickboxing, I got a lot better. You can see the same thing when you look at how current professional or semi-professional mixed martial artists "branch out" their skills -- most or all of them will still have a favorite style and a preferred skill set, but there is no one truly world-class (today) who is not "well-rounded" in at least some rudimentary way. Yet if I tried to step into a ring with a good amateur MMA fighter of my own weight class, I doubt I could survive more than 60 seconds of 10% of the fights. I am simply not good enough. With 15 years of mediocre training, I am simply no match for them. Yet I cannot really get better, not without a huge investment of time. For me, the "breakthroughs" came with branching out and learning a new skill set (BJJ, kickboxing); that catapulted me with only a fairly mediocre level of investment into a new level. But there is no way I will have a decent amateur competetive record at my current level of training. So I am at the bottom of the percentile in amateurs. Yet all those amateurs who could whip me silly would not stand a chance against a professional fighter. In the professional world, the amount of training these people engage in is disjunctive to a "normal" life -- it IS their job, it IS their life. So even very good amateurs are near the bottom of the percentile of profi fighters. The degree of diminishing returns excludes most of the entire world from ever achieving their degree of excellence. Yet there are a large number of fighters out there who will never be the elite of the world-class combatants. This is probably partly due to "talent" or whatever you want to call a pre-disposition, and probably to the fact that world-class elite athletes are gifted with a "natural" predisposition in terms of physical statistics; it is no coincidence that the elite are, in general, not only in optimal physical condition, but that their condition has been optimized on a near-optimal template: in other words, if I were to train optimally under optimal conditions and with optimal support for 8 hours a day for 15 years, I would be in top physical condtion -- but since I am not naturally strong, fast, flexible, nor is my metabolism optimal, I would not be in world-class form.

So what I am saying is that the elite of the elite are in the very top percentile bracket of at least a few various, disjunctive disciplines. To be near the top of the world class in something like unarmed combat, you will need to master (be more than just very, very good at) two or three fighting disciplines (let's say: one type of grappling, one type of striking, and one type of throwing) and you must have top attributes in at least three or four areas, let's say three or four of the following: speed, agility, stamina, flexibility, strength, toughness, ability to withstand pain. To reach the top bracket in any one of these fields would require a huge degree of devotion; for this reason, there can be no more than a dozen or two people in the world who are in the same league.  

You cannot be the best in everything all the time. A master-class combatant will probably have a very, very small chance of being a good programmer, or a good actor, or good at chess, or well-read, or good at guiter, or good at philosophy, or be particularly beautiful.

Sadly, this post has turned into something of a ramble -- sorry for that. I hope you might glean something constructive from it nevertheless.