Simple answer? It's a way for Blizzard to "balance" pvp without having to completely retool the classes to balance against each other. In the most basic sense, the easiest way to nerf the nuclear pve numbers of dps classes for use in pvp is to apply a damage reduction. Consider, where do mages stand versus a warrior in burst dps in raid?
21:43 - Why do PvE and PvP gear need to be separate?
Lore is also probably correct in what would happen in response from the player base if you eliminated the resilience stat. He's probably very close to the truth in that this whole thing is somewhat driven in response to the players.
The reality of it though is that Blizzard could eliminate resilience on gear. They could make PvE and PvP gear functionally identical again. This would have a ripple effect though on the gameplay. Blizzard would pretty much have to scrap a lot of things though in order to re-establish "balance".
I love this one.
28:56 - What if you got 0 honor for losing a BG?
Again, simple answer..... dominant faction becomes more dominant. PvP becomes much more unpopular and random bg's implode.
How many times have you seen a side at least stick around until the end of a bg that they're clearly losing, just to grab the honor for completion? Without it.... what's the incentive for a group that is clearly getting thumped to stick around? Would you hang around in WSG or Twin Peaks for another 15 minutes if you're clearly outmatched?
Put yourself in the shoes of a person on the losing side of the equation. You've just run 4 losing bg's in a row, you're busted your ass trying to get a win but have still come up short and now have absolutely NOTHING to show for it. What is your incentive to PvP? Your gear isn't going to get better magically without a win, and with PvP gear being what it is, you're simply NOT going have very good odds of winning without it.
Final thoughts.......... (Warning..... Wall O' Text)............................
Really, these questions are tangled together and are just facets of the same issue. Player vs Opponent balance. Whether the opponent is a PvE or PvP foe, you want the PC (Player Character) to be effective against both and you want the PC to be threatened by both.
Blizzard has dug themselves into a nasty little hole with this. Really, it's a bit of a vicious circle in a sense. They WANT to make gear improvements "meaningful" with each tier, but with each tier, that improvement becomes harder to balance out. With PvE it isn't very difficult. You can progressively make bosses with more health and make them hit harder in order to ensure that the PvE player feels threatened and at the same time, feels like they are contributing to the larger effort required to kill that opponent. Most boss fights are targeted toward a certain timeframe. 5 to 10 minutes for a total fight.
The problem however starts to appear when you take those same characters in that same gear, and now pose them against each other. Suddenly, that "meaningful" stat increase has to be dealt with somehow. The PC's, against each other, are sudenly NOT balanced.
Don't believe this? I have a ready example in-game for proof. It's simple. Level 80 - 84 PvP bracket. Perfect example of how gear scaling for PvE creates the problem. A toon at level 80 versus a level 84 can almost be compared to a level 85 in 346 gear versus a level 85 in 397 gear. The stat value increase is very similar in relation to each other. There is that much disparity between the two sets of gear. The situation rapidly becomes unbalanced as the 84 can do so much damage in one or two hits that the lvl 80 is simply not able to survive. The damage output from the 84 becomes such a large percentage of the 80's health, there is simply no contest. Even between level 84 toons, the damage output is simply staggering.
PvP attempts to resolve the ever increasing damage output with resilience. It's just plainly needed if you want PvP to be anything beyond a one-shot, one-skill scenario. The health increases from the gear simply aren't enough on their own to mitigate the issue.
Even if you were to increase health correspondingly, you've now altered the PvE dynamic. What was threatening to a PC in PvE is no longer a threat. The obvious counter would be to increase boss damage accordingly. This generates another problem though with heals. Now the effectiveness of heals must be increased to afford the ability to survive the damage of the PvE boss.
BUT.... as soon as I do that, now I have altered the PvP balance yet again! Now, the ability to outheal significant amounts of damage comes into play. In PvE, you have to be able to maintain a PC against life-threatening amounts of damage..... but when this translates to PvP, you now face someone who is effectively "unkillable".
Worse yet, Blizzard has yet to address the issue of healing. It became quickly apparent that the 10% mortal strike debuff was not sufficient in 4.2. It might have been enough in 4.1. but with improvements in 4.2 gear, that debuff was overcome through the brute force of greater stats.
The issue Blizzard now faces is that with ever-increasing stat scores, they're facing a gretaer problem each time with scaling these things against each other. In some ways, Blizzard cannot be faulted. Did the company truly expect the kind of longevity that WoW has shown? How many other 8 year old games are there on the market that are still growing and evolving? How many other developers have had to contend with this issue? If Blizzard had well and truly known that WoW would survive 10 years and have 4 major expansions, they might have approached stat growth in a different manner. They may have taken a larger scale approach with the idea in mind of a progression across the grand scheme of the game.
What we're seeing is the effects of poor long-term planning. Blizzard is now looking at WoW with an eye on longevity. The problem is, it might be just a little bit late.
TL;DR - Blizzard didn't do very good long-term planning in WoW and have boxed themselves into a corner on gearing, and now are stuck trying to figure out what the hell they can do to fix it without making players (more) unhappy (than they are).
No one tanks in a void.........