Once you have a good game-plan of what to use when in high-rage and low-rage situations, then take a look at your UI and keybindings; there are a lot of extra threat-performance that can be gained or lost from the quality of your setup.

Warrior main tanks have a flurry of different abilities that need to be used in careful sequence to maximize threat and mitigation, so here are some tips.

1. Key bindings: Physically separate your globals from your non-globals to avoid a setup that would every require the same finger to press two buttons simultaneously. Example: I have my important abilities mapped to the keys right around WASD, so my main keys are Q and E. I'm going to set Ring Finger for Heroic Strike and Index Finger for globals: I put heroic strike on Q and then the most common GCDs on E and the surrounding keys: 3,4 and R This ensures that no single finger ever needs to hit two buttons at once. In this setup, the "2" key works very well for Shield Block. If you use CTRL or SHIFT to supplement these (which I do) make sure these bindings are used for things you don't do often (like disarm) because you never want to weave ctrl/shift into a standard rotation. Any ability you use more than once every 10 sec should NOT need a modifier key.

2. Unit frames. Pick a good UI that puts the information you need where you want to see it. Whether its a HUD, or Perl, or AGUF, find something that puts the important stuff front and center. Less time spent scanning the screen means more time spent focusing on rage and cooldowns

3. Get your cooldowns nice and visible. This goes along with #2. Warriors have tons of short-duration cooldowns to keep track of. Other than the global, you've got Shield Block, Shield Slam, Revenge, Disarm, ZRage, Taunt, not to mention your buffs/debuffs like CShout/Dshout/Tclap. This is a lot of keep track of, and the default UI does a terrible job. Personally, I make an extra block of buttons (I use Trinity) that appear in defensive stance and put them right near the middle of the screen. I make these buttons BIG (like 1" square) and only include my important short cooldowns, along with a numeric counter. So now I have these huge buttons that I can watch for the Global Cooldown, and to see my Shield Block, Revenge, and Shield Slam timers, along with longer stuff like Disarm and ZRage.

in raid situations and with the latest rage buffs a tanks runs on 100rage very fast and it is not easy to get rid of this in a optimal way.

what you have to understand ist that there are 3 kinds of specials that will soak rage that can be casted at once.

- sunder, revenge, shield slam, devastate
- shield block
- heroic

heroic is on the next swing timer, while block has no global cooldown. the other abilities are on 1.5sec global cooldown.

if you have excessive rage you need to do your best to keep all this 3 things running. using macros helps but using optimal keybindings is key imo. you need to be aware when a ability is ready, how much rage you have and what to do now.

Something people fail to mention is that shield block costs rage, The single most important thing you should do as a tank is manage your rage bar effectively and not just spam ability's in a pre determined fashion as it's not always the best most effective way.

For most trash in karazhan swap gear around a little, Stick some +hit/+crit gear in, Tanking with a feral druid? take a agility pot and stick a stone on your weapon and your looking at 23% or more crit with raid buffs in full tank gear.

Some short questions since I am in a pretty similar situation as the OP - I rerolled and hit 70 like 10 days ago.

1. How big is the difference between a prot and a non prot spec in terms of TPS? I often see pretty huge figures I can only dream about (granted, running only normal mode instances seldomly fill your rage bar in a sufficient way )
2. I am sitting at about 52 % amor mitigation, 480 Defense, 11,7 k HP and a little bit of additional block/dodge (though my emphasis is clearly on stacking HP). Presuming I respec to Prot, is this sufficient to tank Heroics as well as to MT a new Kara group? (Armory will show my farm stuff unfortunately, otherwise I would have linked my profile there).

1. I don't honestly know, since I haven't tanked as non-prot since 2.0 came out, but I would say you gain about 40-50% more threat from being prot spec. I really do not think it is viable to MT as a non-prot warrior past curator or so. Nightbane, and Prince are going to present major issues for your aggro gen, and that's not to speak for their burst damage, and the mitigation you lose from not being prot.

2. You stats are good enough to MT all of kara except Nightbane and Prince. You can tank those two with consumables though. I'm assuming you will cross the 490 def mark with anticipation? Otherwise forgot what I just said. I really can't speak for heroics as I don't run those too often.

Thanks a lot for the quick responses. I will cross 490 def indeed with Anticipation, else I wouldn't think about tanking Kara anyways As I said, I will respec once we walk into these instances since I only went to a non prot spec for repgrinds and questing for cash.
Also I don't anticipate seeing the Prince or even Nightbane for at least 3-4 weeks (and if I'm proven wrong, Titans and armor pots will probably help to bridge the gap I guess).

CC will be our main problem in terms of heroics since my core team is pretty hybrid heavy (moonkin, shaman, holy priest, me and x - all of them being rerollers )

I'm unconvinced that threat is an issue for nightbane or prince.

First let's examine Nightbane:

This fight is anything but a DPS race, people are in no real rush to kill him, outside the landings the ground phases are extremely stable. As the tank, you are probably the only person avoiding fear (stance dance or fear ward) giving you more time actually doing stuff to the boss, which helps you stay ahead. Finally, on the landings temselves - well no one should be doing anything, and you should be able to burst enough threat to lock him on landing regardless of spec.

Next let's examine Prince:

Prince only has a single special threat mechanic of note - he randomly enfeebles people who aren't at the top of his threat list, so the tank needs to be #1 on threat at all times. Now I'm confident a tank even without prot should be able to out-threat healers at Prince. So the only issue should be DPSers pulling ahead of the tank. Fortunately the Prince fight only becomes a DPS race for the last 30% of his life. Thus you simply need to have your DPS hold back and let the tank build enough of a threat buffer beforehand so that they can burst heavily for the last 30% (ideally they'd build the buffer in phase 1, so they can push through phase 2 at a reasonable pace, and go all out in phase 3.)

Sorry about the slightly off-topic question.

If rage was not a concern at all, what would be the highest threat cycle a warrior could use?

Shield Slam, Revenge, Devastate, Devastate, Repeat. Heroic Strike every swing. Shield Block every cooldown.

What ever happened to Shield Bash? I always used to tell tanks that it was one of the high threat-per-rage skill that should be used when it was up. Did that change at some point?

You are correct in that Shield Bash is decent threat per rage. It is not however very high threat per second. It is lower TPS than Sunder. It's good for low threat situations. I like to Bloodrage + Shield Block, then shield bash Nightbane as he's landing at the start of the fight, because I am low on rage, but need to do something. Not hitting Shield Block at the start of the fight has led to some relatively quick wipes.

On some mobs you can use Shield Bash to daze the target, allowing Heroic Strike to deal more damage, and thus more threat, however from what I've observed, only a few trash mobs in Karazhan have not been immune to the daze once you get into a raid environment.