rawr says it 30 dps upgrade from needle and a 6 dps upgrade from DC.. if you've got the time you should post in Mihir's fix my dps gear thread. as you get more gear and hit the arp softcap, your trinkets might end up being WFS and NeS.. but see what mihir says
scorpion is 17% uptime on a 10sec buff, so you can do sh*t at all with it in a real fight. It is in thoses situations rawr cant give you an appropriate answer other than '30dps higher'. In my opinion it would have benefits you way more than 30dps. You'll get the whispering fanged skull an other time with little luck
there is a reason feral druid's go for soft cap with an arp trinket. rawr can give a reasonable answer, but considering all trinkets have a proc.. even if it doesn't value trinkets correctly, they would all be devalued to the same amount more or less