I don't think base PvP defense is so much about addressing the gear gap as it is about giving Blizzard better knobs to control the speed of PvP combat. Right now, players in full PvE gear kill each other very quickly and players in full PvP gear kill each other more slowly. In Mists, those speeds should be closer together, since the system is no longer relying on resilience to slow down PvP to the intended speed. Instead, PvP gear is mostly just about being better for PvP than PvE gear at the same ilvl (for both offense and defense).
(I say "mostly" because DPS goes up faster than stamina as gear ilvl increases, and they'll need something to compensate for that. So I'm guessing that PvP defense will be weighted heavier than PvP power. For the same reason, two players in T16 PvE gear will probably still kill each other pretty quickly, since base PvP defense will probably be aimed at fresh 90s.)