Now it's time to dig into crit. And not just crit rating - but agility.
From the first article we know that crit rating and mastery rating are basically equal (at least right now) in terms of what they give, and the same amount of crit rating to give 1% crit is the same amount of mastery rating that gives 2.5% bleed damage. That's nice; it makes it very easy to equate them without going nuts.
In addition to that, agility gives crit% as well. It takes 1.8 points of agility to give the same amount of crit as 1 point of crit rating, if that helps.
How does crit help you?
Well, let's see. Crit gives you 200% damage on all critical strikes. This includes bleeds, melee, and any special attacks. The 220% boost on crits is either not implemented or purposely taken out at this point; my guess is the latter. Add the metagem into the mix, and your crits do 206% damage.
For every 1% crit you should in theory get 1% more damage, roughly. That's not exactly true. For starters, there is a cap on crit% for white attacks (76%). There's a soft cap for things like ferocious bite and ravage as well, though that doesn't often come into play. And mostly, it's a matter of degree; if you sit at 0% crit, 1% crit will increase your damage by 1%. If you're at 40% crit, the crit boost only increases your overall damage by .7% (since you can't make your crits...uh...crit again). That sounds awfully close to the mastery bonus in terms of damage potential - so are they equivalent?
Well, without knowing what the crit rates at 85 are going to be, it's hard to say. Chances are that a 40% crit rate is pretty high, actually. At level 80, assuming ICC gear you get absurd amounts of crit thanks to every bit of arpen converting to crit (almost) - but that crit decreases very fast. Instead, we'll look at median damage values for crit rates:
0%: 1% crit = 1% dps gain
20%: 1% crit = .83% dps gain
30%: 1% crit = .76% dps gain
40%: 1% crit= .71% dps gain
50%: 1% crit = .66% dps gain
Note that this is the case for bleed damage too - as your bleed damage multiplier increases, the overall damage increase each point does is less relative. The overall damage increase from a raw standpoint should the the same though, and note that in order for bleed damage to keep relative pace with crit%, bleed damage has to be around 40% of your overall damage.
Anyway, that's part of crit's success, but the neat part is when you talk about the extra combo points generated. Here's where we get more meaty bits.
The cycle in cataclysm is mostly unchanged from wotlk; you keep savage roar up, you keep rip up, and you keep rake up while shredding when you have spare energy. Rip always at 5 CP. SR when you can (and as I'll point out, it's actually a bit more efficient to SR early). The change comes from the endless carnage talent. Rake now will have a duration of 15 seconds (up from 9) and SR will add an additional 6 seconds to its duration regardless of combo points. Rip's duration is unchanged, and because the glyph of rip is being changed to a straight DPS boost instead of a duration boost, the maximum duration rip will have is 22 seconds.
This means in practice that you must generate 5 combo points every 22 seconds to keep rip up - and do three shreds in that time as well. In addition, you should be keeping Savage Roar up. For ease, I'm going to assume a 5CP savage roar, which means 40 seconds total. Realistically this means that you need to be generating 15 CP every 40 seconds or so just for the basic rotation.
That doesn't sound so bad until you look at the energy that takes. In 40 seconds you'll have 400 energy with zero haste, along with another 60 from at least one Tiger's Fury. You need energy for two rips (30 energy each, so 60 total)and a SR (25 energy) in that time, and we'll assume you're a pro at keeping rake up too - so you need energy for 2.6 rakes (90 energy). That leaves 285 energy for shreds, and shreds are 40 energy each currently.
In other words, 7 shreds. You have 2.6 rakes, 7 shreds, and you're needing to generate 15 CP in that time. The effective crit % required to keep that up is 56% if all you did was that. Now, you'll hopefully get at least one OoC proc - probably 2, so let's assume that. Even so, in that case and assuming no extra CP get wasted (going from 4 to 5) you need an effective crit rate of 30%.
So forget about ferocious biting; you won't have the CP generation. In fact, if you're below 40% crit rate, your rotation is going to be pretty horrible. Rake is the most efficient combo point generator you have, but you won't be raking that often compared to now (every 9 seconds or so vs Cataclysm's 15 seconds or so). What that implies to me is that crit is going to be very, very important early on.
Which makes sense; some of the basic advice from most ferals in the early and midtier of WotLK was to get crit at 50% at least before going for arpen, and the same advice applies here as well. Except we don't have anything like arpen in terms of boom or bust stat, so it's much more forgiving to go for.
One of the things I expect is some criticism for this post as I assumed 0% haste - which isn't realistic, not by a longshot. The point is to illustrate how important crit rate is for ferals (especially compared to mastery), not to devalue haste. I'll get into this in the next post, but as a teaser - the above assumed 0 haste. If you assume around 20% haste (which with stats and buffs is about right) you get 100 energy every 8 seconds. That means that in 40 seconds time instead of 460 energy, you get 560 energy, meaning that even in the worst case scenario (no OOC procs) you get 2.5 more shreds than the 0 hasted situation - which requires an effective rotation crit % of only 25%! if that sounds awesome, it's because it totally is. That it increases your OoC procs by 20% and increases your melee damage by 20% doesn't suck either. But like I said - we'll get into that next time.