That rough stat priority strikes me as correct. Expertise is itemized against main stat, not against the other defensive stats, so we can use the same math that we do in PvE. (in other words, you want as much Expertise as you can get; after that, worry about defensive stats) The only tricky bit is we have to make a different assumption about the proportion of melee/ranged attacks vs force/tech. Normally, I would have put this around 45% m/r, which is what I surveyed it to be a few months ago. However, the large number of snipers and marauders in PvP today likely imbalances this a bit, and so I'll tip it to a 60% m/r, 40% f/t balance.
Without further ado, here are the ideal defensive stat distributions for tanks in PvP (at level 55):
It's worth noting that, due to the heavy reliance on shield/absorb, shadows and vanguards will be absolutely godlike in PvP. Guardians are going to be pretty far behind the curve, though they make up for it in other ways (mobility and control).