This is not even an issue. you should always weave acceleration in the same place you would any other ogcd so that you don't clip; after aero/thunder, even if you don't have any procs.

The reasoning is actually quite simple. Even if you get shafted on the 50% chance, jolt II still has a 100% chance to proc impactful, and impact has the same potency as stone/fire. You won't clip your gcd, you won't lose any additional potency to rng(well, in the next few gcds), you'll get your acceleration proc.