Honestly, I tend not to post about other people's posts. It's a principle about avoiding interweb drama. I had enough drama in high school, and I get more than enough in the way of office politics.
That being said, Black Legion Matt has an interesting point about the nature of competition. His statement is something about list variation does not mix with a level playing field. Now, I agree with this to an extent, but I also think list variation is a part of what makes 40k interesting.
Honestly, there is something to this. Games like chess and checkers involve a predictable field of battle, and give each player identical armies (and in the case of checkers, uniform playing pieces).
The only real difference between the respective forces is that one side goes first, and one goes second. Not being a chess/checkers expert, I have to assume that there are tradeoffs between going first and second, and if not, there's at least the 50/50 shot (...I suppose that depends on the playing format? I'm making assumptions here) at getting it. I suppose you could try to go at the same time, but I don't think the games are set up that way, and the difference between first/second is just something that's built into the game.
The bottom line? Since first/second is generally random and the armies are identical, it's purely a case of player versus player.
Frankly, if you wanted to play with uniform armies, you'd either play chess/checkers, or you'd have some kind of agreement with your opponent prior to a game that allowed for variety in army builds. Given the cost of the game and the allowance for variation in builds, I've got to kind of say if you're playing the game, part of you is tacitly in agreement with variation in army build.
So, I'm assuming you're cool with variation in army build. Where do you go from there?
Now, this is much, much easier said than done. Ideally, though, this is the solution to varied armies. Now, all the armies abide by the same Force Org charts (3 each Elite/Fast Attack/Heavy Support, 2 each HQ, 6 ea Troops; required 1 HQ/2 troops). They also abide by the same points level.
The stuff in the game (troops, vehicles, monstrous creatures) dictates the type of destructive tools you'll need. Now, honestly, here's where I think a lot of the variation gets screwy. The easy example is the mighty melta weapon. Some armies have access to it (Tau, the Marine armies, Imperial Guard, Eldar, Witch Hunters, Daemon Hunters) and some do not (Tyranids, Necrons, Orks, Dark Eldar).
Consider the effectiveness of melta weapons against vehicles (which are good because of Vehicle Damage Rules that say a 35pt Rhino can take the same number of AP1 hits as a 250+ point Land Raider) and the prevalence of vehicles in lists that can take a lot of them (Imperial Guard and Razorback-spam being a couple of the prototypical examples) or Tyranids, who can roll with a heap of T6 multi-wound monsters. It's easy to see that the people that can bring and effectively employ such weapons are in good shape.
So, having access to the right capabilities is crucial. Now, here's where we get to the meat of the problem. How does your army handle various types of threats? Vehicles are just the easy example, since they're prevalent. If you want another sample, look for psychic powers and/or psychic defense, and the effectiveness thereof.
The simplest example here is the Ork army. What do they have for anti-tank at range? Lootas. (Ok, they can take missiles as well, but considering you get only a few per squad, want to take large squads over multiple squads most of the time, and have a mighty BS2...yeah). Problem? AV13 and 14 at range are issues. So, how do you kill heavier armor? Assault it with...power klaws. Either by having your armored kanz walk up and punch, or committing a squad full of boyz and hoping the one Klaw can do the deed. Neither of these are attractive.
The other answer involves Deffrollas, which is committing a vehicle to a 12" move and hoping it can do some S10 hits to a heavy vehicle. Full stop, end of story, those are your options. And your psychic powers? A random power of questionable utility, and no meaningful way to stop others from casting powers.
I don't want to use Orks as the buttmonkey here, but they're just a simple example. They're lacking a couple of capabilities that make it hard to build a balanced ork list. I'm not saying it's impossible, but when someone like Space Marines can drop 200 points on a troop unit that has a meaningful anti-tank weapon (BS4 multi-melta), a workable anti-troop capability (a flamer, a bolt pistol and 8 rapid-firing bolters) and a transport it can fire the anti-tank weapon out of (Rhino not moving) then, well...yeah.
No, we covered that; it's probably not what people are paying $300-500+ on an army to play when a chess set is probably a lot cheaper. The core, then, is to give everyone the capabilities they need. At that point, it is on the players to bring all of the tools. Let's be honest, while some people play more (or less) 'cut throat', everyone plays to derive some enjoyment out of the game, and most people don't enjoy getting monkey-stomped.
Hell, most people don't enjoy giving out a monkey-stomp; you either wanted a challenge or feel bad for the other guy (and either way, it's somewhat counterproductive, since crushing people mercilessly and just gloating about it aren't healthy for the hobby).
So, what's the answer?
SIMPLE! (/sarcasm). Symmetrical capabilities. Everyone needs a reliable way to accomplish their missions: you need both access to competent anti-infantry and anti-armor capabilities, and you need to take them.
I don't care how good a player you are, if you bring as many power-armored bolter guys as you can and I bring a couple land raiders and some tanks, you're probably screwed. Now, the Space Marine codex is a solid book with plenty of ways to get the capabilities you need; you as the player need to bring them.
So, we've solved the game's problem: you just have to bring the right tools for the job. Now, the issue: not everyone has access to the tools. Necrons are the easy example here: no transports, one option for troops that's basically a slower tactical squad sans weapon options, and one gun with a strength better than 6. The rules for 4th edition made them fine, the rules for 5th? Not so much.
So, what's the Necron player's situation?
Honestly, pretty crappy. You either try to find a build that works while you lack some crucial tools (I'm not saying necrons need psychic powers, but a psychic counter would be nice...) and hope that your player skill is enough to make up for it, or...you get a new army.
Considering the cost involved in starting up a new army (even using e-bay or other discount methods, that's a few hundred bucks) I think that's a pretty crappy answer. The other option involves getting an update to the rules, but GW's release schedule for codices is...sometimes slow (I'm looking at any Dark Eldar fans that have kept their armies for the past however many years...).
Even my pet Tyranids were in the same situation not too long ago, and honestly? I had a 'nid army, sold it off, and then got back into it when the new book came out. Did I lose my love for the 'nid fluff and spontaneously recover it when the book came out? Or, did I get tired of trying to kill vehicles by running melee-fexes at them or hoping to glance them to death with S6 AP-, or when my best long-range gun was S8, single-shot, BS3? (Pro tip: it was the latter, and dying a little inside when the rules said I had an uphill fight).
And this is the part where I propose a comprehensive solution, right? Well, honestly...the best I can think of is that GW should consider updating the rules a little more often. 4th to 5th edition was a major sea change, and the armies that had access to the right tools could be more competitive.
If you give someone a few tools to tide them over and have some semblance of competitiveness, you're going to keep that player happy, and they're more likely to keep them in the game. The alternative is to have people impose artificial, arbitrary limitations on the game, which isn't necessarily going to make the balance any better, only different.
Update the freaking books more than once every few years when you radically change the rules, or it ticks people off, and keep people angry long enough and they probably stop dumping hundreds of dollars into your game...