Balance in the Arena is about 5 things, which to me go in a rather neat order of growing importance. If Blizzard wish to get perfect (or at least better) balance, they need to address/fix all of those issues to a certain degree.
I know I'm probably going to get some disagreement here, because 'It's not skill, it's gear!' is the favorite defense of the bad players who's bad gear is their excuse for losing. While Gear is a factor in Arena, ultimately, it's the less important one - let me explain.
Gear is extremely important (And in fact the most important factor) at entry level and low rating. No matter how good you are, you will not break past a certain rating without proper gear. That's the truth. The great majority of players are in that rating range, so to them, gear does indeed seems to be what it's all about.
However, as you get gear, and get past the low ratings... you quickly realize that everybody has gear. when two full Vengeful gladiator geared team face each other - Gear is a non-factor. The guy who is at 2.4k Arena rating, did not get there because of his gear - his gear stopped giving him an edge 400 points ago.
While there's always exception (looking at you their Warglaives Rogues!), for the most part, gears go from being the most important factor at lower level, to being a non-issue once you pass a certain rating cap.
There isn't really a problem to begin with. As mentioned, gear is only a balance factor early on, and Blizzard has done a good job of making entry level pvp gear as well as making pvp epic much more readily attainable. Yes, it takes forever to get Full S1 from honor, but this is a mmorpg, there's always going to be some kind of grind.
That being said, I really dislike the idea of rating on gear and the PR that followed. I believe the first created the Team Boosting problem and made everything worse and that the later is just damaging a system that wasn't that flawed to begin with.
All rating on gear did was make the pve QQ'er shut up (and even then...) but from a competitive point of view, it does gives the edge to people who get them first. A 1999 team face a mirror match team who's at 2000. All things being equal, the 2k team will win. It really shouldn't be that way.
Granted, the stats difference on the shoulders is small... but the ones on weapons are massive.
We've all seen a game being lost because someone didn't switch target fast enough, didn't interrupt at the right time, didn't use CC properly, etc. Skill plays a much bigger factor once you get out of the entry level where gear is what determine everything. Skill can make up for worse gear in many case... it's quite possible for lesser geared folks to beat other team by outplaying them... and on my way to 2k, I had to beat several team who already had their shoulders (and my partner is using S1 shoulder and karazhan weapon/offhand), yet we prevailed on many occasions.
However, this is WoW. Not a fps. Not a fighting game. The skill cap isn't that high. There's only so much you can actually do to make yourself a better player.
For the most part, the solution here is the solution for the next issue.
The RNG, random number generator, is simply way to powerful in this game right now. As you get higher and higher rating, where people are both geared and skillful, it quite often comes down to who gets lucky, and entire games can decided in the blink of an eye based on nothing more then the RNG.
Things like getting Surefooted's 5% snare resist to make you resist a Frost Nova, a priest's talent saving him from a stun while he's doing a clutch heals, a Druid resisting a imp CS, etc - the deeper you go into the game, the more winning seems to be based on the luck of the draw.
Possibly the greatest offenders here, are warriors (At one time, rogues were just as bad, but combat mace is hardly viable anymore). Mace Stun and Imp Hamstring wins game, there's just no way around it. Warriors are either killing machine that will all but 3 shots you... or annoying pest you can more or less ignore because they can't touch you anyway. The same warrior with the same team will go from being one to the others, in the course of several fights... why? Because in 1 fight, he's getting Mace stuns and Hammies out every time he touches you, on the other? Mace stuns aren't happening. It's totally ridiculous and in great part why warriors are considered a 'face roll class'. The most terrible warrior can get lucky and Stun 3 people with a Whirlwind or get 2 imp hamstring proc in a row, and there's nothing anybody can do about it.
As frustrating as it is for non-warrior to get hit by a 'well timed' mace stun, I'm pretty sure it's equally frustrating for warriors when their mace seem to refuse to proc or procs are pointless moments.
Make the RNG matter less, up the skill cap of the game. As many 'proc' ability in the game as possible should be made into a 'on use' ability with a short timer. The game should be proper timing and judgment of when to use an ability, not spamming something in hope of getting procs.
There is such a thing as a hard counter to your composition. They are time when you'll fight a team that is more or less designed to beat yours and you will lose no matter what, unless they do a major screw up (which I suppose, goes back to skill). This is possibly the hardest aspect of the game to balance, and true balance might never be achieved without sacrificing each class's originality.
Keep trying to make change and hope you get it right. Rogues and Druid need a lot of fine tuning atm...
It's actually pretty damn ridiculous that rogues can arena in full pve gear and do well... that's a class problem however, not a gear problem.
When it comes down to it, at the highest level of play (and before that too), when you have two strong comp fighting each other, with fully epic'd out players who share equal luck (or bad luck) with RNG... it all comes down to which race you picked.
Yup, put that in your pipe and smoke it if you ever said to someone 'Race don't matter, take the one you like!' - you've given out terrible advice.
Perception, Will of the Forsaken, Warstomp, Escape Artist, Stoneform - Can all win the day. However, some of them are simply better at it, and/or better when taken with a certain class/comp.
Make it so racials don't work in the arena. Or my favorite, make racial learnable/trainable by other races.