Is it useful to drop the t9 4p for t10 2p? Since its a 4% dmg loss then, and alot more RNG incoming.
If so, what item should i grab along with the shoulders?
Personally I went with shoulders and gloves, since then you trade two +spirit pieces out with hit/crit crit/haste pieces. You could also say that you shouldn't go for gloves since the new VoA boss will drop them, but frost emblems will be raining down on us soon enough and it shouldn't matter much.
It's also not a 4% dmg loss, more like 3.2% (wrath + starfire makes up about 80% of my dmg in a fight). 2pT10 also works on all your dmg and should be about a 3.5-4% dmg increase on avg if I got my ppm on OoC correct.
Yes, it does add an element of RNG to your dmg, but not something you would notice a whole lot during a 5 minute fight.
Checked some logs and the dmg increase ranges from 2,25% to 3.72%, with one freak accident where OoC only procced once during the fight. So my conlusion is that for a short fight (sub 3-min) it can be a bit of a pain, but it will on the other end of the scale be heaven on any aoe fight.