So there's been a bit of discussion that went on in Acherus, and from testing I found that Clawing Shadows is equal to Castigor
on everything except single target.
To list things very simply
-In pure patchwork single target
Castigor beats Clawing Shadows by ~17k dps.
-The test for aoe was done as 4 target patchwork, which comes out to the same result as Beastlord/Hectic Add Cleave sims.
It shows that CS (with SI) vs Castigor (also with SI) are both roughly the same dps.
Now what this overall means, that unless you're on a pure patchwork fight
taking either Castigor, or Clawing Shadows is roughly the same outcome.
If you get more Haste/Crit gear, go for Castigor. If you get more Haste/Mastery gear, go for Clawing Shadows. Even from just 2 targets up, Clawing Shadows will match Castigor's dps.
These below are
clickable links showing results.
Castigor - Single Target
Clawing Shadows - Single Target
Castigor vs Clawing Shadows - 2 target Patchwork
Castigor vs Clawing Shadows - Castigor was optimized for aoe by Alaiz and I ran all three lvl 90 talents with CS to see the highest.
So all in all, this means that both are very much viable. if you prefer one over the other, go for it and try to get that type of gear.
Personally I will be going with CS, as the range on it generally fits raiding better and eliminates more problems/potential for lost dps than Castigor (obv, imo).