To Arcane or not to Arcane.....That is the question......

No, it’s not because of Armor Penetration alone. Stop saying that.

*sigh*

Now that that’s out of the way, let’s get on to the meat of this discussion – why you drop Arcane Shot from your normal stand-still rotation. (Bear in mind, and I’m gonna say this in bold letters: Arcane Shot is still extremely useful when moving. Keep it easily keybound and at hand. This is only talking about a stand-and-shoot encounter like Patchwerk/Festergut.)

To really get into the meat of why you drop Arcanes for Steadies, we have to first learn how each shot works.

Steady: A steady shot that causes unmodified weapon damage, plus ammo, plus [RAP * 0.1 + 252].

Arcane: An instant shot that causes [RAP * 0.15 + 492] Arcane damage.

Steady is a lot more complex than Arcane, but it’s not too bad. The “plus ammo” quip is due to the fact that ammunition isn’t a damage increase, it’s a DPS increase, meaning that the amount of damage it contributes is based on weapon speed – or it would be, if it weren’t for normalization. This occurred way back when in patch 1.7, and it basically means that for any special attack (Steady, Aimed, Chimera), 2.8 is used in place of your weapon’s speed for calculating both damage contribution from RAP and from ammo.

So in math terms, this means that each shot looks like:

Steady: rand(weapon bottomend, weapon topend) + (ammo DPS * 2.8) + (Ranged AP * .1) + 252

Arcane: (Ranged AP * .15) + 492

Let’s look at those with my personal stats, unbuffed, from Armory.

Steady: rand(541, 887) + (91.5 * 2.8) + (5214 * .1) + 252 = 1570.6-1916.6 damage

Arcane: (5214 * .15) + 492 = 1274.1 damage

Now, at first glance, this looks like a no-brainer to not use Steady. But… Steady is physical damage, and thus mitigated by armor. We know, from extensive testing, that a WotLK raid boss has 10643 Armor, and using the armor formulas from WoWWiki, we get a damage reduction percentage of 41.13%. This means that, with no ArPen or any debuffs on a target, only 58.87% of my damage goes through. Suddenly, that 1916.6 damage Steady is now:

Steady: 1570.6-1916.6 * .5887 = 924.61-1128.30 damage

Arcane: 1274.1 damage

Makes a world of difference, right? But wait… there’s a few things that Steady has in its favor that Arcane doesn’t. First off, there’s the wonderful Glyph of Steady Shot, which is another 10% damage on the top. On the top end, this helps to push Steady over Arcane in its favor, but it’s not enough in all cases.

The biggest factor that can get Steady to prevail, aside from reduction of armor, is Piercing Shots.

We already have Mortal Shots and the Relentless Earthsiege Diamond powering our critical strikes, which means that our crits do 237.8% more damage than a normal attack, due to how RED and PS interact. But… Piercing Shots causes Steady Shot to bleed for another 30% of the total damage it dealt, essentially adding another 30% modifier to a critical attack. Let’s look at what that does to the post-armor numbers.

Steady: 924.61-1128.30 * 2.378 = 2198.72-2683.10 * 1.3 = 2858.34-3488.03 damage

Arcane: 1274.1 * 2.378 = 3029.80 damage

Already, Steady’s looking better and better! And we haven’t even begun to get into raid buffs like Sunder Armor/Faerie Fire, Mangle (which increase that bleed damage from Piercing Shots), and concepts like Armor Penetration.

The summary of what I’m trying to tell you is this: There are many factors that go into removing Arcane from your rotation – mana usage (Arcane doesn’t benefit from Master Marksman), weapon damage, critical chance, armor penetration, and raid buffs. In all things, use your tools to determine what is the best course of action for you. Do not listen to anyone who tells you “oh you can drop arcane at $NUMBER arpen rating” or “oh you have to have $RAID_TIER gear to drop arcane” or any supposed “guideline”. Do what mathematically works for you in your raid setting with your gear and your raid composition.