Hunter talent · row 2 of Survival, from level 15 (10 with Talented 5/5) · Physical

Improved Wing Clip Rank 1

Improved Wing ClipRank 1

Gives your Wing Clip ability a 7/13/20% chance to immobilize the target for 5 sec.

Game files · build 1.60.1.70291Read straight from the WoW Forever beta client.

Compared with Classic

Classic tooltip

Gives your Wing Clip ability a 4% chance to immobilize the target for 5 sec.

What Blizzard said about Improved Wing Clip, each line checked against the files.

Partly
Improved Wing Clip now has the correct chance to activate and reduced chance to activate if using ranks substantially below your current level.
The files Improved Wing Clip's aura proc chance (19228) went from 4% to 100% in 70291, so the tooltip's 7/13/20% is no longer cut further. Nothing in the files lowers the chance for low Wing Clip ranks, so that part is server-side.
Improved Wing Clip Wing Clip (rank 1)Wing Clip (rank 2)Wing Clip (rank 3)Development Notes, October 8
Matches the files
Improved Wing Clip: Now only takes 3 talent points to reach maximum 20% chance.
The files Improved Wing Clip (19228) has 3 ranks at 7/13/20% (talent curve); Classic needed 5 ranks to reach 20%.
Improved Wing Clip Class deep dives: Hunter and Druid