It would be helpful if you posted a gear list. I've never found being hit capped important unless a fight gimmick requires it. Threat is fairly trivial these days with Tricks and any 277+ weapon will sky rocket your threat even further. It is nice as an option I guess but I don't' find it a great choice.

I'm not sure about your threat evaluation either. You lose an absolute truck load of crit from the change, something along the lines of ~4% if my quick math is right, and thats just from the weapon (assuming Bloodfall Heroic for Cryptmaker Heroic here) which also contributes to Savage Defense uptime.

[Ikfirus's Sack of Wonder]
[Soulthief's Braided Belt]
[Armbands of Dark Determination]

Those along with the Rep Ring are your best bet if you want to cap out Hit and retain 4p/armor. Granted, in BiS you won't be hit capped but there are fights like Saurfang, Sindra, LK, etc... where hit rating is needed for Growl. And then there's a glyph for that so.... it's really just preference.

Used Rake without 4xT10 (no Crits), without proc ring, proc trinkets, idol, with scougebane on weapon (zero effect, no proc):
Tested dueling on my Feral Mate (Cat Spec, Bear Form, 4xT10)

Results
Without Barkskin and Enrage 1174 Damge per Racke tick
With Barkskin and Enrage = 802 Damage per Rake tick

(802 / 1 174) * 100 = 68.3134583

4xT10 Enrage is additive, correct?

I'm pretty late to the discussion but I totally agree with Cliffjumper. It's a pretty rare occassion that growl fails in my experience and you pretty much know through experience what mobs are going to ignore taunts in the first place like Skirmishers in AN. I'm a druid tank who regularly tanks for healers in training , Frenzied is a great glyph. I'm still trying out a third major glyph but I'm really leaning to SI.

I've used Cryptmaker to tank Lich King in both 10 and 25 man, I don't see what the issue would be. I gemmed full stam for the fight, so I find the extra threat to be pretty handy.

First off I am wondering why people are using the AV rep ring. Is it only for the hit cause it seems like a huge sacrifice in the way of mitigation to not use the Heroic loop. Unless the proc is higher then i think and avg out to be more then the 532 base armor of the loop.

If you want to be hit capped for your melee swings you need 263 hit rating 230 with a heroic presence. You would need the heroic Bracers of dark determination, heroic Treads of the icewalker, heroic The belt of the merciless killer and sack of wonder. to meet the 263 cap and you can lose bracers or boots (or the belt if you have the heroic chest) if you have heroic presence. I would get the Heroic frostbitten fur as it is the bigger upgrade to armor and stam. Maybe the heroic toskk's maximized bracers if they have the second socket as it is a 43 agi upgrade.

not upgrading any 2 of those items is a minor loss to keep the hit up: the following are all number going from heroic toc item to heroic ICC. the numbers below are what is gained by the switch.

Dark Determination vs Toskk's: 19 armor, 17 stam, 43 agi (pending the heroic toskk's has 2 sockets if they don't then it is a 13 stam loss)

Treads of the ice walker vs Frostbitten fur: 29 armor, 22 stam, 22 agi

Belt of the merciless killer vs sutured cinch: 24 armor, 22 stam, 22 agi

The second thing I see revolves around growl. If this is all you worried about i think you have to look at the numbers different. and remember that spell hit and melee hit are a little different. While it takes 32.79 hit to equal 1% melee it only takes 26.23 hit to equal 1% spell hit wich growl is subject to. So if all you are worried about is growl then the numbers are a little different cause there are many thing to help spells as opposed to melee.

17% = 446 hit
17% - 8%(glyph) = 237 hit
17% - glyph - Heroic presence = 210 hit
17% - glyph - HP - 3% misery/imp FF = 132 hit

and to put it another way for people to do their own configurations.

17% = 446 hit
Glyph = 209.85 hit
HP = 26.23
Misery/Imp FF = 78.69 hit

in a nut shell i plan to keep my heroic loop of the twin valks, heroic Treads of the icewalker and Heroic Bracers of dark determination for the foreseeable future and keep my Heroic Belt of the merciless killer for the time i do not have a Heroic presence.

As I said last time this discussion came up (2 pages ago), Survival Instincts is not mandatory, not in the slightest. I find it the weakest of our 4 Major feral glyphs. I do carry a stack around with me but that is more for fights where Gylph of Maul is bad to have, which is mainly Deathbringer heroic. I've never found the extra health all that useful except to be able to break 100k HP. I've yet to encounter a point where I popped SI and died anyway so don't favour this glyph at all.

As for Glyph of Growling, there are many points where a failed taunt is either a wipe or at least a really bad thing. Saurfang Heroic a failed taunt is going to generate a lot of rune power, even if its just 1 hit extra before you AoE taunt. On Dreamwalker Heroic towards the later stages the adds are coming so fast that you need every ranged pickup tool you have and a missed taunt here likely means people start dying. Same goes for Soul Reaper and the other add/tank swap fights in there.

Well we 2 tanked H: Dreamwalker 25 and I couldn't have done it without Maul glyph. Helps enormously on H: Deathwhisper too. Also nice for Lich King raging spirits in P2>P3 transitions though its a small use. My point is though that a small use from Maul glyph trumps the near zero gain I've seen from SI glyph. It is personal preference and you play to your strengths (I can see the argument for SI if you're stuck with bad healers) but it annoys me when people claim these things as mandatory.

Well I could understand the argumentation that SI glyph is not required and you swap it in for a nice support glyph like Rebirth (Save Rez, if you are on a 2-Tank Encounter, which you are mostly) or Berserking (DPS). Furthermore, it might seem funny to you but SI Glyph helps lot if you want to BR while tanking. Barskin, Enrage, SI => Casterform, BR... it does work.

Glyph of Maul is really only useful at some rare fights:
Deathwhisper (Growl useful but not required),
Gunship (on your ship, Growl replaced with Maul),
Dreamwalker (Maul very useful, Growl also, but SI also if your healers focus Dreamwalker at the very end right before she reaches 100%),
TLK (Growl also very useful imho)...

So for harder fights it is probably only Lich king where one might drop SI for Growl and Maul, on the other fights its more the one or the other (or you may trade SI for something useful, like Berserk or Rebirth, but I think SI still does a better job, for instance at Professor, I think he parry hastes and at one time did 100k dmg (3 stacks up) to me in <2sec).

A full 1/3rd of the current end game isn't what I'd call rare. I'd also say on all those fights you list Growl is better than SI too. I tested it out tonight. A normal SI will give me about 84k hp whilst a glyphed one puts me at about 100k. Whilst you may see "Woah, another 16k hp!!!" but that 16k is only useful if you're ever dying during unglyphed SI, along with a small FR boost. I don't have that issue so for me SI glyph is usually wasted.

Several of the adds in the Dreamwalker Fight are level 83 (Blazing Skeletons, Gluttonous Abominations, possibly others). You will need 8% melee hit in addition to the Growl glyph to ensure all taunts land, just like with a boss.