It already was 30%. Look at your skill tree ingame lol.
No he's talking about whatever the imp equivalent of combat trance is.
Right now Ataru Form has a 30% chance to proc opportune attack and 100% chance to proc combat trance.
While combat trance is active Blade Storm is an auto-crit.
In 2.0 Combat Trance is tied to opportune attack, so only a 30% chance to proc combat trance, and the autocrit that comes with it (though now Combat Trance gives you your focus back when you Blade Storm).
That ain't a small change. That's a huge nerf to Combat Burst.
Meanwhile, smash has undergone a rebalance at worst. Smash hits a bit less harder, but everything else hits a lot harder.