Inaiwae, I think that once you get enough crit you don't need a ton more to smooth out anything. It may change your gearing choices (going for agi over strength and favoring crit rating) but it's not a make-or-break rotation changer like shredding attacks or KotJ is.

Grimcat, I'd drop feral aggression in a second. I wouldn't take imp mangle at all (as cat or anything else). Take natural reaction instead.

It's less important once you have enough to maintain your rotation, and secondarily because the higher your crit chance relative to your AP, the better AP becomes in terms of marginal returns for DPS. It's certainly true that you'll get more FB opportunities when you're drowning in combo points--but your FB is also already critting most of the time (as you note indirectly), so again, the DPS return on crit continues to fall. Obviously more is better than less, but if you're choosing between two equal Ilvl pieces of gear, where one has Str and the other Crit, their relative worth depends on your current crit/AP ratio.

As a minor note, haste also generates combo points, assuming you have OoC (and why wouldn't you?), but not terribly well.

It does not take "a few seconds" to get behind a mob. You are either chasing after it and are already behind it, or you are running at it and can easily get behind it in a tenth of a second extra than it takes to get to it. If you are in front of the mob and have time to attack twice, then you have time to move behind it for at least the second hit (the first one is generally always going to be mangle anyway).

If you are trying to save someone by killing a mob before it gets to them, sure you can mangle it first (then shred). If you happen to pull agro you can mangle again. If you are trying to save someone and 2 hits isn't going to kill it, you are usually better off going bear and taunting it anyway. I agree "some fights it's not about maximizing dps".

Mangle spam is never the best option unless you have agro (and then you are often better off going bear in a raid). I don't see any example you can give where you would want to stand still in front of a mob spamming mangle instead of either getting behind it or going bear.

You're right, it can take even longer.

Some mobs can charge. Charge means they're not where you thought they'd be. You move into position, the mob runs away, and you're left chasing after it. Mobs can also change their facing. The tank pulls, you move behind, someone gets aggro, you move again, the tank gets aggro, you move back. You waste enormous amounts of time getting into position and staying in position for a shred.

I won't even get started on the room full of oozes. Stay behind the mobs is really not advisable.

In my experience, trash pulls in Naxxramas are sometimes sheer chaos. Mobs are charging everywhere, flipping back and forth between targets, and occasionally dropping dead. When you've got a dozen mobs through your raid, saying "stay behind the mob" is like saying "stay dry in a rainstorm." Maybe it's not like that when you have Naxx 25 on farm, but for guilds that are breaking in it can be insane.

There were more than a few times last night when I couldn't even find the back of a mob to get behind.

So according to this thread: if I can't get behind the mob, in order to maximize my dps I should switch to bear form rather than manglespam. I am skeptical of this claim, but I will give it a shot.