No "Chance on Hit:" procs work in Feral form. None. Ever.
The only procs that work in Feral forms are those things that may proc when you get hit. Like
this.
So regardless of the type of proc (stun, damage burst, lower armor/resist), nothing "Chance on Hit" will work for Feral Druids. Not too long ago I wanted to /slap a guildie of mine into Oblivion because he carried
Princess Theradras' Scepter and he was a Feral Druid... He could've used a spoon and get equal results.