PVP gear for bear tanks is not a bad option at all as long as you're not replacing Clefthoof slots with the PVP S1 options.
S1 Head & Shoulders for bear tanks are the single best options in the game pre-T4 or getting higher arena gear. I don't care what anyone says, I'd rather see a tanking druid in Gladiator Head and Shoulders than any single PVE blue. Not only does the PVP gear offer a substantial amount of Armor, it also offers a large amount of stamina, meta socket (Head) or other sockets (shoulders), all while offering a fairly nice chunk of crit immunity in the form of Resilience.
And the thing about Resilience for bear tanks is that it works quite well. Druids can not parry/block so those are two aspects we don't get to take advantage of when using Defense. In some cases it's quite easy to just use Resilience + Agility since if you're using resilience you actually need less of it than you would need Defense to become crit immune.
Vindicator Waist and Wrist pieces for bear tanking are easily in the top 3 choices a bear would want in the game. I absolutely love mine for threat generation as they truely excel over most other options in the threat department while still maintaining themselves as a decent choice to tank in. For bigger fights they may fall back a spot on the charts, but they'll still maintain themselves as an option to use when you're trying to tank easier content where your dps classes can really unload.
For the OP, you really just have to try to find the appropriate balance of stats. I'd think that if you're using vindicator wrist/waist/feet that those are probably the best pieces for those slots until you can get into T5 content, but don't quote me on it as I'm not a hunter. If you can manage a piece of S3 it will likely be better than a lot of the alternative options for you depending on where your guild is at for progression.
For the most part though you'll likely want to try to only use PVP S1 gear in slots that you're having a really hard time getting an upgrade for. Just don't go too heavy on the PVP gear without carefully considering all the stats that are appropriate for your class (+hit, AP, Agility, or w/e)