1. What is arms?
If you read the opening, you basically read my answer. But to be more comprehensive, arms is the tree of the warrior class that focuses more on weapon skill and personal discipline. Arms talents fall into general categories like the various weapon specializations, strikes and strike improvements (Mortal Strike, Improved Heroic Strike, Improved Overpower, Taste for Blood, Unrelenting Assault, Sudden Death) and precision abilities (Impale, Deep Wounds, Trauma, Blood Frenzy). Basically, arms is all about focusing on one weapon and trying to improve your ability to use it.
2. What are the benefits of arms?
Arms is a strong leveling spec. You don't need to wait to get a talent, you just grab a 2h weapon and go. Most of the early tier arms talents will either help your DPS or your ability to avoid damage at the starting levels (I am in fact leveling a tauren warrior as arms on Zangarmarsh just to see how it goes, and so far it goes just fine even in starting greens without heirlooms) and the spec only gets better for leveling as you go. Arms is in general easier to gear for than fury for a DPS warrior and provides raid utility through the Blood Frenzy debuff.
Historically, arms is one of the most popular warrior specs due to the original 31 arms 5 fury 15 protection and 31 arms 20 fury specs used in the level 60 endgame as tanking and DPS specs. With the release of Burning Crusade, it became much more difficult to tank endgame with a spec lacking in protection, but arms thrived during rage normalization as a PvP spec and was a potent force throughout the first four arena seasons. Today, while arms has fallen in representation it's still a popular PvP spec thanks to the Mortal Strike debuff, the mobility of Juggernaut, and the potent Bladestorm ability.
3. What are the drawbacks of arms?
Unless geared to the absolute hilt and played by a master of the 'arms rotation' (some prefer to call it a priority system due to its somewhat random nature) arms DPS tends to fall behind fury at high levels of gear. While arms is still a strong PvP spec, it's also a relatively vulnerable one and kiting is fairly easy for most ranged classes. Arms does expect you to stay on top of your various abilities, so if you're unwilling or unable to keep track you'll fall behind.
4: What are the stats I'm looking for as arms?
When you are leveling, worry about strength and crit. Once you arrive at level 80, the following stats are your priority:
- Hit rating: you want 263 hit rating (8% hit) to completely cap your white swings. (If you're a draenei, you can stop at 7%, which is 230 hit rating.) Once you get there, stop. You don't want any more hit.
- Strength: unless you can push the hard ArP cap or get close, Strength is still most likely your best bet for DPS as an arms warrior. (Soft capping with an ArP proc trinket should be achievable while still picking up strength gear). You will most likely gem for strength as an arms warrior unless there's a good reason to gem ArP like the hard cap or soft cap with a proc trinket.
- Armor Penetration: I'd put ArP just behind strength, depending on gear and caps. While I hate pointing you at spreadsheets and programs in a 101 piece, for the purposes of deciding if you should gem ArP over str, you really need Landsoul's spreadsheet. As many comments in the fury piece last week mentioned, it's really the best option for working out when you gem for ArP over str or vice versa.
- Critical Strike Rating: I'm simply not going to go into the 'crit cap' and why it's not really a cap but is important (it involves the attack table, glancing blows, block and parry and dodge, the relative value of expertise and a whole lot more) but you can read a summary of it on this page if you scroll down. It's less important to arms than fury anyway, because the most hit you'll need is 8% and you shouldn't gear for more.
Unlike fury, arms is not terribly concerned with capping expertise due to its reliance on Overpower as an attack. Since Overpower activates when an attack is dodged and you're attacking from behind anyway (no blocks or parries to worry about) expertise stacking will actually force you to purely rely upon the talented Taste for Blood procs. Don't run away from expertise, just don't worry about capping it either.
So for priority, get hit to hard cap (7 or 9% depending) and then stop there. Strength will be better than ArP unless it isn't (consult a spreadsheet), with ArP beating Crit, and Crit beating Haste or Expertise.
Next up, we talk talents, debate weapon specializations, and talk about why you'll be DPSing in Battle Stance now (which old time DPS warriors might be confused by).