Hmm? Survivability, sure, but Hit Rating > BV always.
In theory yes. However for a new 70 tank gearing up for heroics by collecting his first 70 blues, tank gear with hit rating is quasi-non-existent. BV gear on the other hand is more abundant.
It's important to understand the context, because giving someone the impression that they need to go for gear that's out of their reach could have them potentially ignore or skip the gear that's immediately available as part of their "normal" gear progression path.
For new 70 tanks, blue tank gear with Stam/Defense/Str/SBV is the first step. Building survivability is the priority initially, and SBV providing both threat and mitigation is probably the best stat to aim for after Stam and Defense at that stage.
If your in blues then focus on survivability and increasing your threat which BV will help you out a lot in both areas. If your starting to get epic'd out with badge/kara/mag/gruuls gear then start focusing more on Hit/Expertise as threat will become more of an issue especially in a 5 man..
At the moment my 5 man gear has 142 Hit, 37 odd expertise + as much BV as I can get in. I also use some DPS pieces like the Red Belt of Battle for extra threat and hit rating.
The other day I tanked normal BM with all DPS gear accept for the last boss. It was a lot of fun and I also topped the damage meters . So different from when I first walked in there.