PvP welfare epix, people earn them through performing in Arena or Battleground, even a loss is a step on the road to gear development, barring ranked items all gear is available given sufficient time. In contrast PvE there is no gradual development, there is no gradient but rather a stark line, to get gear you can either down a boss or you can't.
Fundamentally though it is clear that this situation doesn't work for helping progression, most guilds won't kill Illidan, and most people won't get their full Tier 6 gear. This drives a lot of competition and whining, why does a PvP player get their Season 3 gear when a PvE player can't get their Tier 6 for the same investment. Lets look at the sets (gratuitous images for the win!):
|Season 3||Tier 6|
Both look the same, both have similar ilvls, so the major difference is the stat allocation and the method of acquiring this gear. Lets say however that because PvP is a more fluid environment than PvE its gear level alters more dynamically with time to give a reason to seasons, and that we want to reward PvE players for their time input as well as simply being able to down bosses, same trick as PvP, you get "better" gear with a rating, but there is a progression path for those that can't get that rating.
So taking this theory Blizzard did an ok job, we had the badge gear, but what if it was rep / points / honour based as well, we have the Karazhan and Scale of the Sands rings which get better with reputation from that faction, why can't the Tiered gear sets scale as well? So our started T4 set maybe the 4 pieces rather than the 8 or so in a full arena season (we have to distinguish here, T5 > T4, T6 > T5, thats our rating mechanic, you need to down the bosses to get the starter piece). So we start with our basic gear, its a bit like other gear its level, but has the set bonus and normally a Meta slot at least in the helm. Now as we progress, each time we kill Prince we get "Slayer of the Eredar" rep, once we kill him often enough (and selected other mobs likely) we can up its quality, in the end we can have the Exalted T4 set as slightly better than the starter T5 set, this means you go into a new set of instances with gear to conquer it, or at least give it a good go. Those guilds that rush will still not have the "perfect starter gear" for that instance, but it means that farming those few bosses you can do now has a point, your gear can advance to give you a shot at the next level.
A system like this could of course be backed up by Badge of Justice loot, Tier token trade-ins (for those with more rep than they need, or a specialist type of that class) and of course the old favourite the Random Number Generator loot.
Of course there will still be complaints, both sides have their equivalent of "welfare" epics, its not to say its a bad thing, but rather that there needs to be gradual way to move people through content, suddenly slamming in badge upgrades works, it helps a lot especially for those of us with little gear optimised for us, however its a stop gap solution that doesn't fit well. Repping up your gear, or having your server progress and open up different levels of badge gear capped at the current highest guild's progression such that a server progressing well will continue to progress, while those that are capped don't have a huge gap in the middle of their ranks making it hard to keep guilds moving.
The PvP "welfare" system works, as it was once said people are "on the path", more concerned with the abrupt barrier in the path that is the Season 4 requirements than the aspect of "welfare", and this is what PvE lacks, every content level is a barrier, it would be equivalent to never getting any of the next season's gear until you hit a 1700+ rating (or whatever the PvP equivalent is for T4/T5/T6). The lack of a gradual access to the gear makes making that transition hard, like PvP its a lot harder to enter the higher brackets without the gear, and to get the gear you really need the higher rating.
Without the gradual trickle that is "losing 10 games a week" PvE is a start stop gear roller coaster making progression very difficult for a time, then suddenly becoming very easy as you acquire the gear from downing that boss a few times, or passing a mark such as the old Hyjal and Black Temple attunements that open up loot bosses. However these marks are equivalent to opening up 1/3rd or so of a season at a time and pretty much handing it to guilds, most guilds that reach past these marks down the "loot" bosses within a few attempts making it massively easier to return to those that were hard. Making the gear more of a trickle system with people achieving their expect level of base gear (the tier sets) before moving on means a lesser reliance on the RNG system, and far better progression for guilds that cannot simply zerg content because they maintain an even course (if somewhat slow) towards actually downing the final bosses without requiring nerfs to the content. Of course other issues may present, but no longer will you be barred from progressing because your tanks got really unluckly and never saw their drops, or be stuck for recruits because a mark presented a huge barrier on your server, there will always be people on the path.