I'm not even going to attempt to tank anything in Northrend yet, because I'm almost entirely sure I ain't got the health or the armor, or even.. the level, to be able to hit the enemies. So, say I quest to 70 and then try to go into dungeons, what's a good benchmark to hit for with my health and armor IN bear form?
I started out as a lvl 68 on my DK recently. The health was pretty low about 12k and I was crittable. All you can do is give it a try. See if you can find anything with more stam. If it don't work out to well, wait til 70 and have fun!!!
You *are* able to put out some threat since I believe Ingvar is level 72 and he isnt red to you, now that you are 68. Try tanking when you cant hit him, thats a challenge ><.
But anyways, I would say do a majority of the quests in Howling Fjord or Borean Tundra, whatever you choose. I am 74 on my warrior, and in the full Cobalt set I have around 13k health, give or take. Your health will always be higher than mine, so I cant say a target health or armor.
As far as I can tell, your spec seems fine. You dont really need the glyph of growl for random dungeons until you start tanking T9-T10 bosses.
Mostly all your gear has stamina on it, which is good. Trinkets are questionable..but theres not a lot of options yet. Give it time. Clear howling fjord before you start tanking again if you want the gear. Dont be afraid to replace BC blues with WotLK greens, 90% of the time they are better. Give it time. Atleast you won't be critted :]
Benchmarks aside, if you want to start tanking, you need to modify your spec. You will lose some dps, but you'll pick up the mitigation talents. 3/3 in SOtF will also ensure you're no longer subject to critical hits. I understand the desire to buff your talents for more DPS output in cat form while questing, but in bear gear and spec you still do more than enough damage in cat form.
As an aside, I frequently quest in bear form. I just pick up a few mobs at the start, and pull a cluster of them through a subzone swiping to keep their attention and adding new mobs as I pass them. When the last one is down, you just loot the trail all the way back to where you started. You can easily down 30 or 40 or more in some zones without taking a break. That's 30k, 40k or more xp unrested on top of whatever quests you might complete.
The heirlooms are nice, but in their absence I'd recommend that each piece of gear have some stamina on it.
P.S. Berserk & Mangle (Bear) is nice when you've got a huge pile of angry stuff in front of you. Just hit Berserk and tab mangle through the group and watch them drop.