I think the reason T6 geared guilds are having issues with the timed event is because gear isn't a massive factor in ZA especially regarding the timed event. It's about pace and playing nearly perfect. It doesn't matter how strong your gear is if you don't know how to pull the trash mobs quickly.
It's still early. It's like the 45 min strat run. Some pick up it quickly others it takes a while to learn. Sure it certainly helps to have better than full Kara gear in doing it, but it's more about knowing how to execute the pulls than being able to do Infinite + 1 dps.