Ghostcrawler chimes in with Blizzard's analysis of how this happened in Wrath of the Lich King. He explains how PvE content was made very accessible, thus giving many players access to powerful gear (or weapons) while introductory PvP gear came much later and was difficult to get. This resulted in players entering Arenas with low life and no resilience -- you can probably imagine how that turned out. It didn't help that classes were dealing too much burst to begin with, which led to class changes through several patches. A final point he mentions is how BC granted a lot of Stamina that wasn't replicated in Wrath, which made players "feel a little fragile initially".
Ghostcrawler prefaced his post by saying that Blizzard increased the budget of Resilience -- which means it eats up a lot more item points for a lot less bang -- because PvP gear in The Burning Crusade was too attractive. This "forced a lot of players to feel like they were supposed to head to the Arena," in order to be competitive. Ironically, this isn't any different now despite the different tiers of PvP gear available. The best gear is still only accessible through Arenas.
This is the problem. Unless you compete in high level Arena play, you're unlikely to feel the benefits of full Resilience. You simply won't have access to the necessary gear, specially in the current environment where it takes a whopping 82 Resilience Rating per 1% of Resilience. For casual PvPers -- and even though Blizzard never quite acknowledges them, always considering Arena play as their baseline -- PvP will always be a burst affair.
The addition of a set bonus to the crafted PvP sets is a case of too little, too late. It's a good move, but by the time Patch 3.1 rolls around, it will be time for Season 6 and anyone wearing the crafted PvP sets to Arenas are gimping themselves. One important point that Ghostcrawler made is Blizzard is considering launching the next Arena season at the same time as the first tier of the next raid content, which should help narrow the gap between PvE and PvP gear acquisition.
Resilience didn't exactly fail in Wrath. It just didn't get to players on time. Many players are slowly feeling the effects of toned down burst as well as healer dominance (once again). Particularly in high rated Arenas, it has become rather difficult to burst anything down. Healers are essential to comps and with the Tournament Realms granting access to the best Arena gear, players will be able to feel the difference. Current gear is still a ways off from the Resilience soft cap, but it's getting there. Season 6 is just around the corner, after all.