Since it is "all damage taken" I would assume it doesn't matter if it's before or after. Case in point, you have 50% damage reduction from armor, 30% DR from AD. A mob hits for 2000:
Armor reduces it to 1000, AD reduces that to 700.
AD reduces it to 1400, Armor reduces that to 700.
BoSanc wouldnt help much anyway, and bosanc is before all the other mitigation (but get bosanc to get holy shield). Back on the note of AD, if you have 14000 HP, AD would only work when you have less than 4900 health. If you're down there, you're probably going to get 1-shotted either way.
As far as your build goes, imp ret aura wont help much on the boss fights, where you will want devotion aura up. Ret Aura is only really helpful on multiple mobs.
Anticipation...if you have 490 defense without it, dont bother getting it. If you need the talent points to get to 490 defense, then use it.
Dont rule out BoK, it's more useful the better your gear, and is great especially in 25-mans where you have people speccing for certain stats (such as survival hunters).
Reckoning, while being a great talent in PvP or soloing, is not good for raids. It's good you left that out.
Avenger's shield, unless you have the talent point to spare when you're done, is also not necessary for raids. You can always have a hunter MD you and then pull, or just pull with arcane shot rank 1 and pick up the adds with concecrate.
You can also look in holy, the 5 points in divine intellect would be very helpful to increase your mana pool. Although I'm not sure how much your mana pool would suffer while you get healed up from raid boss damage.
5/41/15 is what I would recommend.
One more talent I'd like to look at:
PoJ - Good, but I believe not necessary on most fights.
EDIT: Jack, it's 30%, not 35% (haha I made the same mistake I just corrected it BEFORE I posted it).
Edited, Dec 28th 2007 2:48pm by skribs