This was my old raid tanking build, before my account got hacked. it differs from what greenroom had slightly in being designed more for tanking raids. HS is maxed because as an AC/Stam tank in a raid, I was generally swimming in rage, and would use HS to dump rage for threat on a fairly regular basis. Imp. Bloodrage for one reason--opening combat with a shield slam. Burst threat like nothing else can provide. I picked up anger management for the extra rage over the course of a fight. Over prolonged encounters, anger management actually comes out to a fair deal of rage. 20 every minute is an extra shield slam and revenge every minute, which is actually a good bit of threat. No imp. shield bash because it was a fairly useless skill inside of raids, and I didn't have any need for it in 5 mans. My build also did not include either imp. demo shout or, most of the time, imp. defensive stance. Our OT used imp. demo, so I didn't need it, and imp. defensive stance is really a useless talent until dealing with SSC/Eye levels of magic damage. For those nights I would generally drop 2 points from Imp. Shield Wall and one point from Imp. Sunder, and drop them into imp. Defensive Stance for the evening.
That was, however, before, and this is now. Like greenroom said, Imp. Sunder is about to apply to devastate, which is amazing. Before, imp. Sunder was on the more useless side of talents. It was something I would use in a boss fight 5 times, to get to full damage devastates, and rarely on trash. 15 or less rage saved over the course of an encounter just wasn't enough to merit the talent points. With the new system however, I would take the two points I used in Imp. Shield Wall and put them into Imp. Sunder, making
this build.
In response to the OP, watch your DPS. If they're jumping onto the mobs too quickly and that's what is causing you to have agro problems, tell them to calm the hell down, and wait for the tank to get some threat. With a mage main, I'm sure you're used to having to hold back at the beginning of a pull. If you have ample time to get threat, and still can't maintain rage and agro, try tanking more mobs. Honestly, more damage makes tanking easier for a warrior, as long as the healer can handle it. By the end of when I played, I was doing no CC in the majority of heroic runs. Know how much damage the mobs do, know what you can handle, and honestly take everything you can. Use the CC you have, but my no means should you rely on it. As a tank, I always felt it was my job to control the situation, and whatever was directly in my hands was something I could make sure didn't go bad. If a pull requires you to sheep, or sap something, do it. If you can go without it however, I tended to always go without. It allowed me to focus more easily on my job when the mob was right in my face, whacking away at me, rather than having to watch the group of mobs on me while also making sure the sheeped guy didn't break and go after clothies.
Your build looks fine as far as I'm concerned. You're levelling, so there's absolutely no reason whatsoever for you to go prot. I would honestly just work on reigning your group in and maybe your rotation. As non-prot make sure that revenge never goes unused if it's available, and on multi-mob pulls, use thunderclap every time it's off CD. It puts out as much threat as sunder does, but it hits 4 mobs, and also slows their attack speed, making them cause less damage to you. It's pretty much win all around. It honestly sounds like it's just the hiccups of learning how to really tank in the outlands, and doing that as a spec that's not optimized for threat. You'll play, and you'll get better at it.