One might not think that there is any difference between tanking instances and raids, beside the mobs hurting more. But because the mobs hit so much harder it makes some talents and glyphs more usable, even necessary to use, compared to when tanking instances. Remember what I said about tanking? It's about being able to take the damage and keep the aggro. As your gear gets better and better, so does your capability to take damage of course. For all heroics currently out there, a gear set of about 4500 gs is enough as long as your healer is alert. For the latest raids however, ICC and RS, you'll most likely have to use something other than just your gear to be able to take the damage. The reason for this is simple, raid bosses often use special skills to do extra much damage, especially designed for you and others in your raid to have to use cooldowns with proper timing. It is what make them tougher than instances.
Some skills are baseline, like Shield Wall, other skills are talented, like Last Stand and Vigilance. Some skills are for taking damage, some skills are for keeping aggro. How necessary each skill is depends on what you want to do. So let's look at the differences between raid tanking and instance tanking.
Instances, meaning heroics, are mostly about being able to keep aoe threat. Not only are most packs in heroics consisting of several mobs, most people will expect you to do fast and smooth pulling. If your gear is decent, taking damage will be less of an issue, and you should therefore focus on talents and glyphs that will help you with threat on several targets.
Raid tanking is mostly about having cooldowns to use when things heat up. Seriously, most of the time you just stand around staring at the boss, what makes raid tanking even slightly difficult is knowing when to use the proper cooldowns (there are always exceptions of course). Therefore you should focus on getting talents and glyphs that will help you with taking more damage. It might sound easy enough, but there are some debatable areas here.
Leave Cleave Alone
One of the biggest debates regarding instance-tanking is whether you should use cleave or not. The idea goes that when using Cleave instead of Heroic Strike, you'll hit three targets at once, thus making three time the threat for the same cost! That's not entirely true of course. Although both Cleave and Heroic Strike are onswing-skills, aka used in the same way, they work rather differently.
If speccing into Puncture, Cleave costs 17 rage (plus the rage you "lose" from using your swing on a special attack, which isn't an issue really if you're tanking). To get the most from those 17 rage you should also spec into the third tree in fury, Improved Cleave which increases damage on Cleave with 120% (there is also Incite, which buffs both Cleave and Heroic Strike). One probably wouldn't spec that far into Fury for any other reason, which means Cleave costs some talentpoints to optimize. Cleave does hit three target at once, which is three times as many as Heroic Strike of course. Cleave has no special modifier for threat however, so it doesn't do extra threat like Heroic Strike does.
Heroic Strike also needs talents to be optimized. Most people spec Improved Heroic Strike if they tank with Heroic Strike, but if rage isn't an issue you don't have to (unlike with Cleave). So if speccing into Puncture, Heroic Strike costs 12 rage, down to 9 rage with Improved Heroic Strike. It only hits one target, but instead it does so with extra threat. So the question is really, does one want low threat on three targets at once, or high threat on one target at a time?
It might be obvious which side I'm on. Personally, I don't think Cleave is worth the hassle. Since Cleave doesn't make alot of threat, it is meant to be used as a fast aoe-mob-gathering-threat. Some people seem to think that using Cleave will save us from having to retargetting constantly. Thing is, we already have such tools that do their job just fine if we know how to use them - Thunder Clap (especially this), Shockwave and Demoralizing Shout. The issue rarely is about keeping aggro from aoe damage, but from point damage on different targets.
Say you're fighting four mobs and the mage does aoe, the rogue nukes target A and the warrior nukes target B and does some aoe. Keeping aoe threat here won't be the big issue, trying to keep aggro from target A and B being nuked will be. Cleave won't help you with that, at all. Heroic Strike on the other hand will (and Shield Slam, Revenge of course). What you have to do in this situation is shield slamming and revenging different targets, while keeping thunder claps and heroic strikes rolling. If you want to avoid having to retarget you've chosen the wrong tank class. One of the charms of warrior tanking is optimizing your rotation based on what you're fighting. So leave Cleave.
Some tanks go deep into arms and spec Deep Wounds (pun intended). Yet again the main reason is for getting better threat. Yet again however, I don't think it's worth all those talents. Unless you have really big issues keeping aggro you shouldn't have to spec this. When doing instances mobs die too fast anyway for you to have to use more than what I've already talked about - Thunder Clap, Shockwave and Demo shout. When doing raids you'll hopefully have a bunch of competent threat transferrers aka hunters and rogues to help you with aggro. Also people tend to mind their aggro more if they know they'll be one shot and maybe even wipe the entire raid if they accidentally pull it from the tank. Being able to keep high aggro is more important than it sounds, since whatever threat you're able to push out sets the limit for how much damage (threat) the dps can push out. More aggro = more damage = good. I am sure I have mentioned this before. I don't think that Deep Wounds will make that much of a difference though that it's worth all those talents, since I think having good threat is mostly about using a good rotation, and having a good amount of hit and expertise at that.
Some talents are nearly worthless in raids, but more useful in instances, and vice versa. Of course, there is nearly always trash to be dealt with in raids, and situations in instances where you need a talent more often used in raids, but overall it is like I've already said - instance = keeping aggro and raid = taking damage.
One of these talents is Concussion Blow. It is basically useless when fighting raid bosses since they're never stunnable and as far as I know CB doesn't work as an interrupt either. The only reason you'd want it for raiding is to get down to Vigilance, which I know alot of raid tanks don't spec either. I like it however since the 10% threat transfer is pretty great no matter if you're instancing or raiding. So even if Concussion Blow isn't any good for raiding I still think it's worth it to get to Vigilance. For instancing Concussion Blow is a neat tool, and definitely worth one tp.
Iron Will is a talent that, contrary to unpopular beliefs, is more useful for instances than raiding. You'll rarely be stunned or charmed when doing raids, this does however occur rather often when doing instances. Often enough to be necessary? No, I don't think so, but it isn't a totally bad talent. For instancing. So if you're really annoyed with being stunned this might be something for you.
Reducing the cooldown on Shield Wall (because that is what matters here) won't be necessary when tanking instances. You rarely use Shield Wall unless something in your party sucks, whether it is you, your gear, someone else or someone elses gear. Hopefully those issues are transient. When tanking raids however, reducing the cooldown on Shield Wall equals to you being able to take alot more damage. Reducing the cooldown by 1 minute means that it becomes 20% better, which actually is pretty awesome.
Spare Talent Points
Most tanks grab some points in the fury tree for some extra threat. Even if you don't go all the way down to Cleave, you'll have points to spend in Armored to the Teeth, and maybe some points for Cruelty. When having taken all the talents that you actually need, you'll be left with some extra tp's that you can place anywhere. AttT and Cruelty are simply two talents that are pretty worth placing those spare talents points into.
I think I've covered most question marks that might rise when trying to spec for raid tanking and instance tanking. Thing is that even if you're pretty set on instance tanking, chances are high that you'll do some raid tanking as well, like VoA. Therefore, unless you're dead sure you won't do any raid, having some raid talents are worth carrying around. Raid talents in instances are more useful than instance talents in raids after all.
Here is an example of a spec that works well for both raid tanking and instance tanking.
If you never ever gonna raid, you can place the talents in Improved Disciplines into Cruelty and Improved Demoralizing Shout instead.
Next time (which might be tomorrow, maybe another day) I'll get into what glyphs to use depending on tank setting. I had intended to do it today, but as always I write more than I think I will... No more time!