Berserking for a tank is an absolute no-go, don't go there.
On the stamina vs. threat vs. avoidance topic.
Firstly, I have no clue how threat is for level 70 warriors compared to how much threat DPS'ers generate. You don't want to be in the situation where DPS'ers have to hold back their damage on boss encounters. You should only gear for threat (eg. threat gems or a threat trinket) when you find yourself in that sitution.
Although, if you are not in this situation where you constantly struggle keeping agro on bosses and your threat is always way up there, you have three options:
1) Gear for avoidance
2) Gear for stamina
3) Gear for a mixture of avoidance/stamina
This mainly comes down to personal taste. As a former main tank of a raiding guild, I always geared for full stamina on progress situations. Especially at level 70 right now, where mana isn't a big concern for healers, it's very effective to go all out on stamina. Doing this also gives the healers less stressful moments. You can effectively take 2-3, or maybe even more, hits from a boss without dying. Once stuff is on farm, you are safe to go for some avoidance in the mix. Again, personal taste. I used to start matching socket colors to get the socket bonusus. Using dodge/stamina for yellow, and at this point of the game, strength/stamina for red.
TLDR: While NEVER having threat issues on bosses: Full stamina for progress, mixture of stamina/avoidance on farm status. If you do have threat issues: gear for a bit of threat.