From MMO Champion...
Item - Druid T8 Feral 2P Bonus (Class: Druid) -- The periodic damage dealt by your Rake, Rip, and Lacerate abilities has a chance to cause you to enter a Clearcasting state.
This is HUGE!
To refresh your memory the old 2T4 Proc returned 20 energy. This will basically give you a free special on your next attack which as we all know is more than 20 energy.
Depending of course on the proc rate and internal CD this is potentially a bigger deal than the old 2T4 proc and I am sure everyone remembers what a huge deal this was. It was OP enough that Blizzard had to remove the 2T4 bonus @ 80 and scale back the proc rate after level 70 to make sure we stopped wearing 2T4 as we went into Wrath content.
I would assume with the proc happening from periodic damage it will happen a little less and that they are going to make sure through the proc rate that it is not as OP as the old 2T4 but as a feral druid this bonus has to get you excited about wearing T8 4 sure.
And look at the 4 piece bonus...
Item - Druid T8 Feral 4P Bonus (Class: Druid) -- Increases the duration of Savage Roar and Survival Instinct by 8 sec.
This is one happy Hybrid Feral Druid (Soon to be dual spec Tank/DPS feral druid). I mean I have been really happy with my Tanking and DPSing ability since going with a Hybrid build, check it out... top 5 on Thaddius last night (WTB Ret Pally Nerf :P or DK faceroll ability :P)