I'm an Arms Warrior. My current spec is often referred to as Arms Max (max damage) and is a hybrid of Arms/Fury. It includes a bit of Flurry and Dual Wield Specialization. I'm still one of the few DW sword holdouts, but I'm leveling 2H slowly. Still, I like swords and my current spec is modified for that specialization. The reason you see so many Arms Warriors on WoW, even though everyone wants Protection Warriors, is that we're terribly versatile. Most Arms specs have a HUGE toolset on which to draw and can fill many rolls in a party.
Now, Arms Warriors are NOT tanks. I've run into a few that think they are, but please, don't go into to tanking situations thinking you can do it because you can sword and board and wear plate. That would make you a Paladin.:) Under 70 you can probable get away with it most of the time, particularly if you're spec'd with some Protection. I certainly did. But the truth is you don't have the resistance, resilience, threat capability, and mana efficiency (for your healer) that a proper tank does. If you try to tank with an Arms spec, make sure you have an awesome and understanding healer!
As I leveled to 70, I found myself in plenty of tanking situations. Arms is better as off-tank (OT) and main assist (MA), because we can also add dps, act as temporary cc, and intercept mobs that come off the main tank. Still, more often than not, it was me strapping on the shield and going toe-to-toe with the big nasty monster. So here's some thoughts on how to manage in the tank role when you're spec'd for Arms.
First, an obvious: What is tanking? Tanking is when a player draws aggro onto herself, and holds it, while other players heap on the damage to take the target(s) out. Tanking requires a group effort. This is not about soloing, though these principles nicely apply in groups of two or more. Your job, as Tank, is to be sticky. You "get sticky" by generating Threat.
This is pretty simple...
1. Puller (usually the Tank, but can be anyone with a ranged attack) pulls the group of mobs.
2. Tank takes aggro on all mobs and Shield Bashes the designated Main Target.
3. Tank then Thunder Claps to grab aggro on the other mobs and hits main target with Sunder Armor. The healer can now begin HoT (Heal over Time), though it's a good idea to have a HoT on the MT before he pulls.
4. cc takes out the marked targets (usually casters and ranged attackers). This step will many times come before combat starts. That out-of-combat cc is often called a "sheep pull." The down side is the tank has to work hard to get aggro away from the "sheeper."
5. Main Assist starts dps'ing the main target.
6. Tank switches to next target and does one full rotation (See below) on it. MT continues to switch targets, does a rotation on them, and Thunderclaps to hold aggro.
6. Everyone else joins in on MA's target.
7. Mobs die in an orderly and systematic manner. Very kind of them.
All of the above happens in about, oh, 10-20 seconds. Tops. Which means you have very little time to grab aggro and get sticky.
Arms Tank Rotation
Button spamming will wear your fingers out while tanking. Your global cool down should never get a rest. This spamming is called your "rotation." This is tricky for long time Arms Warriors, because the rotation while tanking is very different. To simplify, it's:
Auto Attack, Shield Bash, Auto Attack, Sunder Armor, Sunder Armor, repeat.
This is in Defensive Stance, of course. Every Sunder, even beyond the five debuff, generates big time threat. Throw Revenge in at every opportunity. When you build up to around 50 Rage, add Mortal Strike to the mix. After 5 Sunders, which locks the target hard, I also throw in my Shouts and Improved Heroic Strike every other cycle to keep them refreshed and add damage. You also have to hit Shield Block every time it comes up without fail. Even the basic version mitigates a nice chunk of damage and your healers will love you more. And we all want healer love. Lots of it.
Tip: Turn on combat notifications and the interface will tell you when Revenge becomes available without having to look down at the button bar. It's on the Advanced tab in the Interface menu. The one you want is Show Reactive Spells and Abilities.
Heroic Strike is a monster threat generator too, but be aware it eats rage. Once I'm in my rotation I rarely find an opportunity to use Heroic Strike, though I have had to pop it out to increase DPS on a boss fight here and there.
One of Arms best abilities is the massive Mortal Strike ability. You can greatly enhance Mortal Strike with Tactical Mastery from the Protection spec. Not only does it reduce the "changing stances" loss of rage, it also improves the threat generated by Mortal Strike.
Until you're well geared, even after level 70, you'll always be short on Rage. So, yes, you may have to wait two Auto Attacks before you can start the rotation. Can't be helped, just make sure your DPS and heals know when to start shooting. You can usually tell them on the 3rd, 4th or 5th Sunder depending on the mob.
Rules of Tanking
Rule#1 - Threat is everything.
Rule#2 - Thou shalt Tank in Defensive Stance.
Rule#3 - Talk softly and carry a really big stick.
Rule #1 is the what tanks do. Our primary job is to generate massive amounts of threat and keep mobs off the squishies to keep them alive so they can do their jobs. Sorry, but given desirable conditions, they're way better at killin' stuffs, quickly, than we are.
Rule #2 is the primary way warriors generate threat. Defensive stance generates significantly more threat than the Berserker or Battle stances. A lot more. If you try to tank in one of the other stances, you will loose aggro. Your dps party members aren't going to hold back. You can ask, but they won't.
Rule #3 is about getting the biggest, baddest dps you can manage from a sword. Either quest it, or buy it. But get it. Don't worry about enchants, or glow in the dark, or how cool it looks (okay, cool is important, but...). Those things are nice, but you have to start with raw dps. You can't enchant up a bad sword. Upgrade your weapon even before armor. Crazy? For an Arms Warrior trying to tank it's a necessity.
When It's Right & When It's Not
When can an Arms Warrior "tank?" Tank 5-Man's no problem. Off Tanking is usually good in most situations. Mobs and bosses "in the wild" usually don't present a problem with the right dps and healing party. I've done most of 'em. :)
If you're tanking a Raid, respec. Do NOT tank Raids, Raid bosses, and most Heroics as an Arms Warrior. Just won't work. Respec to Protection before doing these. You can switch back to your lovely Arms spec after the run.
The Well Dressed Arms Tank
As far as gear goes, there's not a lot you can do to generate threat. The best thing you can do to start as an Arms Warrior is to increase your dps. That means get a bigger stick.
The rest of your Arms gear early on is probably going to lean toward Strength and Stamina. Strength increases the damage, Stamina increases your health and, thus, survivability.
For tanking, though, Defense Rating become Very Important after 60/70. Since Arms warriors in this level range tend lean toward "focus survivability" (resilience, which mitigates spell damage) and damage output (+HIT and +CRIT), you'll be looking at carrying two sets of gear. Your tank gear is probably going to focus primarily on +DEF. The "crush cap" (when a boss's Crush ability no longer works) is 490 Defense Rating. So as close to that as possible, but not over. You can tank with significantly less DEF, but you'll require some really great heals. After that you next primary concern is probably Armor value and Stamina. Higher armor means less damage from physical attacks, and higher stamina is always a good thing.
Finally, you need a good shield. The higher the Block Rating and Armor the better. Try to grab one with a +DEF stat as well. If you're Arms tanking, you and your shield are going to become very good friends.
The Versatile Tank
Arms tanking does have it's place, and if you get good at it, many groups will find you make a great tank for the right situations. You have plenty of side abilities (we'll look at those in another post sometime) to add to the equation as well.
The Arms Warrior, particularly, has to modify their thinking when tanking. Your main inclination is going to be to kill stuffs as fast as you can. But if your dps is busy defending themselves, they aren't killing stuffs. And they're burning mana not killing stuffs, which is even worse. Same goes for your healer. Would you rather have your Priest bumping up your health, or bubbling and smiting mightily? Arms warriors don't think much about aggro when they're adventuring and questing. When tanking, though, that's all they should be thinking about.
The key to being a good Arms Warrior is versatility. Learning to tank properly, by being sticky and carrying the right tools, is a big part of it. Consider it just another tool to add to your 20-slot bag of Arms Warrior Awesomeness!