This is the build that im going to run now, used to play the 31/0/10 but for me that doesn't do much for the team in rated.
Yes the wither spec might have more dps coz you can spam FL but this spec has more utility.
DF is a really good skill to have to interrupt node caps etc if you don't have a stun, pull or sprint available and at killing multiple low hp targets.
Instant whirlwind is so good. Any good player will recognize whirlwind being cast and interrupt it or los if your solo defending something. It also gives the sin/shadow more instant stuns. Sap, stun, spike, ww are enough for you to cap/plant and even stall opponents for teammates to turn up and help you.
Also going back to the dps. Both specs are similar in terms of dps produced. I feel the sins/shadows roles in rated (tanks) are not ment to dps but annoy opponents, you have mara, pt, snipers to dps.