Arms tanks can do some absolutely silly single target threat in prot gear with that talent that removes the cooldown on revenge/overpower. I was using that build to prot solo for awhile just because it was amusing.
It all depends how you go. If you go Arms/Prot you can be a very very viable single target tank, you will have aoe difficulty without some of the later prot tools to help you. Your dps will also suffer vs Arms/Fury.
If you go Arms/Fury your mitigation will suffer a good chunk since you will lose out on your dodge, shield, and armor talents. You will be a completely normal DPSer though when you switch gear.
Its all up to you. Gear and aggro skill will get you further than any talent build for that stuff. Theres no reason a full DPS spec can't tank anything in the game as long as his gear is good enough and he can lock down aggro. We've had DPS warriors in DPS gear offtanking in Naxx just cause their base hp pool is high enough to spam heal. Heroics are a bit trickier cause of all the aoe aggro though. It all depends how zealous the DPS are. In a full DPS spec you are only talking about a small hp loss, small armor loss, and decent avoidance loss.
I don't think there will be issues with single-target threat with this build. AOE tanking might be a problem with the 1.5 minute cooldown on Bladestorm. That's why I picked up Improved Thunder Clap and Incite. The new Glyph of Cleaving which will hit 3 targets would also be very good.
Cruelty and AttT are essential for any DPS build so with your typical 54 point arms layout and the 8 points in fury you really only leave yourself with 9 points for prot. You could probably skim arms down to 53 points (52 if you choose to ignore bladestorm).
If you do 0 in fury the DPS drop is very significant, you lose hundreds of points of AP and 5% crit and also the improved bshout unless you have a paladin covering that. As to how much of a decrease this is it varies at different gear levels but it is going to be somewhere in the realm of 15%-20% vs a pure arms/fury build as you will lose anywhere from 10% to 15% of your AP and 5% of your crit. If you do the 8 points in fury you don't really lose much though but from the tanking end you lose armor. The advantage in single target tanking though is you will not need any threat moves besides HS and Revenge which you can spam indefinitely if you are glyphed for revenge. This has the potential for tremendous single target threat.
Incite means nothing to Arms as you will pretty much never be using Heroic Strike for DPS. Its entirely rend, op, slam, execute.
Your build is a very sloppy arms build. You are missing staple arms talents such as Improved Overpower + Taste for Blood which typically makes up around 15% of Arms damage. You are also missing Sudden Death which is 10-15% of Arm's damage. That combined with your 0 points in fury is probably at least a 30%-40% dps decrease. At that point you may as well spec prot and throw on dps gear.
Your Arms layout will probably have to be something like: WorldofWarcraft.com -> Info -> Classes -> Warrior -> Talent Calculator else there is really no point in even speccing arms. Beyond that its up to you if you wanna try it. With the 8 points in fury all you would lose is the 10% armor from toughness, but thats pretty significant. Like I said it puts you in a hard place. You can either lose 10% armor or 15% of your damage. If you're tanking bosses losing the armor obviously isn't an option but if you are just offtanking trash then you really don't need a single defensive talent at all. Either way, you're better off with a pure spec.
If you are looking to just tank though and are looking for a DPS improvement while tanking then you are looking at things the wrong way. Arms will not provide you any dps benefit in tank gear, only if you switch to DPS gear. The only way you end up with something like that is with a 15/5/51 build.
Compare that to the build I linked... in terms of avoidance and mitigation, I'm missing out on Imp Def Stance, Shield Mastery and Critical Block. But since I'm not using a shield anyway, the last 2 are moot.
The biggest disadvantage will be the lack of armor from not using a shield. DK's and Druids have special abilities to make up for it, but a Warrior doesn't.
The reason why I didn't pick up Taste for Blood and Sudden Death is because I won't be able to use those abilities in Defensive Stance. I'm not going to raid with this build, just planning on trying some heroic 5 mans with it.
Ahhhh I was thinking of it as a recommendation for the OP and not as just a raw tanking build. Yeah that loss of armor is killer. Its the most important thing that ties us to using shields for tanking really.
That build is interesting if you're just going to straight up tank with it though. I wonder if you could threat via slam if revenge isn't lit for some reason. Bladestorm would certainly make incredible aoe aggro too.