While i agree with most points listed here( which is a first for ANY of these socalled guides) I do find your glhpy choice interesting,
personally MS+SS+REND - are the ones ill always take simply for the face that it means you can always have SS up and its not cosing you anything(cept a GCD and if arms is played correctly you have more GCD's spare than a Fury warrior or hunter AUTO ATTACK HOOO) so thats generally always a dps gain in any fight that has 2 or more targets, currently my warrior is only 5.1k gs but ive played a warrior for 12 years on retail, and atleast 2-3 years on molten, and any warrior should know how to play arms simply because the DOT buff they bring, Feral/rogues in your raid would love the utility you can bring at the drop of the hat just by knowing how to swap to Arms and you would still only loose, AT MOST 2k dps which in all honestly, IS NOT MUCH and even then given time and learning of the spec that 2k disparity can be taken down, to about 500dps(Been there, done it got the Tshirt and am wearing it) as it currently stands im beating out 5.5k GS fury warriors and higher sometimes as an "lowly bad dps arms warrior"
Now the specs, Incite spec, where do i start, you lose Wep mastery(given you are still gearing i laughed hard at this) 2% chance for your attacks to be dodged less., Lowers the exper cap EVEN FREAKING MORE, given you should never be infront of the target..and while you do use TC alot, and sometimes HS(not very usefull when you can get an slam into the mix) it adds a little bit of spice to the ARMS warrior with a differant spec, but not the preferance i would take.
now the otherspec, 54.17.0 basic and standardized spec for arms duringh execute stage, and a good build all round, although once again, that 25% dodge is lookin at you and sometimes laughing when you cant get EXPR capped and have to gem or enchant it, or even worse take a worse item just to cap it.
now..you never actually explained why you should play an arms warrior, and its differant for every one, heck my own reason is..my own, but the reason to play an arms warrior is a simple one..
Do YOU want to be that mother ****er who swings hard, hits hard and looks hard? Yes? Then Arms, Arms all the ****ing way.