You shouldn't be rage-starved in high-end content anyway, and with revenge costing 2 rage, TC costing 13, devastate costing 9, and SS costing only 17, it's not an issue.
The 3 points you take out could come from imp revenge, as most bosses are immune to stun anyway. Spending 3 points on something that won't even work is worse than spending the 2 points in imp shield wall, which would work maybe once every hour or two. However, I would not put all 3 points into arms for anger management. Unless you have a fury warrior in your group, 2/5 imp demo shout would help out a lot. (Any more points don't actually work on mobs, so again you are looking at wasted points if you go [3-5]/5).
After that, there's one talent point floating around that I honestly have no idea where to put. 1/2 imp bloodrage, 1/3 imp defensive stance (you may not want it, but that talent point wont do much good in most other spots), 1/5 UW, 1/2 imp shield bash, or 1/2 imp taunt. From what you've said, and what I reccomend, I'd say imp bloodrage would be your best bet. 3 extra rage every time you use it.
Granted, for some heavy casting bosses, you may want to find a way to slip 2 points into imp shield bash, probably from imp demo shout (since a heavy caster would have a weak melee attack), and maybe find a way to put 3 points into imp def stance there.
This is what I would use for the most part, and something like
this for casters, if you feel like respeccing.