I honestly see no point in Pulverize, even for pure Bear spec; maybe it's just from my past experiences in Wotlk, but Bears never have any threat problems, I mean it also helps a bit in getting Savage Defense running more, but SD is still a rather (imo) crappy excuse for a "shield", so eh. Not to mention with the buttload of crit we have just naturally, seems even more useless.
Sort of curious what your spec is, my spec technically leans towards hybrid because I have 3/3 Thick Hide (though I'm honestly not sure why I originally took those, I think it's because I didn't want to die soloing elite mobs way back, but either way it's been a raid saver a couple of times). To give you an ideal, here's my spec:
http://www.wowhead.com/talent#0ZdbGfRurzbfzMcz
Honestly IMO, for better tanking the only thing that's really lacking is Natural Reaction, sure Perseverance is nice and helps, but it's not 100% necessary as (I think) neither warriors or pallys have magic damage reducing talents anyways, and they're still the 2 best choices out there. Infected Wounds, eh that's debatable imo for Bears, though the attack speed reduction could help in ways.
For your spec, do you take Feral Aggression? That's a good place to free up some talent points if you do, as it's only really super relevant for a bit more cat dps (other classes can usually throw up the armor reduction effect, and in the worst case scenario that's just 3 GCDs in cat, for bear it's free threat to use it on CD if you're bored of other buttons). Brutal Impact is largely raid dependent imo; if you have someone else who can reliably interrupt instead of you, I'd take Nurturing Instinct over it since you mentioned you do Tranquility a lot (though how you do it if tanking in bear form, I'm not sure how). As I mentioned above, Infected Wounds is also kinda optional to have as well IMO.
So yeah...without seeing your spec, if you're just gonna be doing light off tanking or 5mans, I'd opt for (in descending order based on what you listed) Nurturing Instincts, Brutal Impact, and Pulverize last. At any rate, the big 3 to have are, in order, Thick Hide, Natural Reaction, and Perseverence; if you can get at least the first 2, you should be able to do most basic tanking just fine, you might not even need the 2nd if you have supremely good healers who don't mind a bit more healing. Just don't complain if they complain you're kinda squishy
