I am in the same situation in where I am normally a tank, but I'd like my Dual Spec to be Arms instead of Fury. Right now, I use an Arms spec to help OT in Naxx (on a 3 tank tea), and DPS when OTs aren't really needed. It works out well in that I do much more damage in this situations than when I was Prot, and my tanking isn't too severely affected.
Anyways, if you haven't checked it out already, I highly recommend reading this guide for excellent starting information for how Arms is played, particularly in comparison to Fury: [The PVE Arms Warrior Compendium & FAQ 1.0] . For example, it seems like you're fearful of being raged starved, but from my own experience, as long as you gear up correctly (hit cap, crit to 35% unbuffed, expertise to -5%) the Arms tree nets you more than enough rage, even against a Raid Boss Training Dummy, to use your abilities.
In regards to Improved Slam, it is extremely useful to have, especially if you have the 2 piece Dreadnaught DPS bonus, but it really is there for filler. In most fights, you'll be preoccupied with handling Taste for Blood overpower procs and Sudden Death Execute procs that you'll mostly just be Mortal Striking as your rage dump in between.
Anyways, good luck in your future with Arms! I too can't wait until 3.1 comes out!
Stay strong. Stay smart. All heart.