you assuming that the fact that more people left prior to 5.0 got anything to do with moving to one gear system, that assumption is not correct at all, they left for many reasons that regards the mistakes and failures that Bioware made over the years and it is not the thread to discuss them all over again. I am a pvp player for the last 7 years, 90% of my game time that is high is pvp , I know much of the pvp community on my home server DM ( and I know many of the pvp players who left ) the bottom line is the pvp community is dying regardless of the gearing system and if you will push out the pve players who come to grind the unassembled components, we will sit in the Q admiring our pvp gear and waiting long long time for a pop.
anyway as Eric hinted expertise is probably back in 6.0 and we can see who was correct about it, I wish it will be you, but sadly I sure we will all cry about it, you can't hold the pvp scene alive with current pvp players only. and if pvp won't give the chance to get the highest tier of gear ,the casuals and pve players won't have any motivation to fill the ranks.