Hunter talent · row 3 of Marksmanship, from level 20 (15 with Talented 5/5) · Physical

Lone Wolf

You deal 20% increased damage with all attacks while you do not have an active pet.

Game files · build 1.60.1.70245New in ForeverRead from the WoW Forever beta client, build 1.60.1.70245.

Compared with Classic

Classic tooltip

You deal 25% increased damage with all attacks while you do not have an active pet.

What Blizzard said about Lone Wolf, each line checked against the files.

Not in the files
Talenting out of Lone Wolf will no longer cause the Hunter to have -4% damage while their pet is active.
The files Lone Wolf (415370) still gives 20% with no pet and didn't change in 70009; the leftover -4% was a server-side bug.
Lone Wolf Development Notes, September 24
Matches the files
Lone Wolf: (New 11-point gold medal talent.) Grants the Hunter 20% increased damage with all attacks while the Hunter has no active pet.
The files Lone Wolf (415370) is a 1-point talent in Marksmanship row 3, the 11th point, and gives +20% damage with all attacks while no pet is out (tooltip). The Season of Discovery rune with this ID gave 25%.
Lone Wolf Class deep dives: Hunter and Druid

69876 Sep 16First beta build we archived. No changes in the client files since.