Look at the mole rat combat scene at 13min17sec into the "Fallout 4 - E3 Showcase World Premiere" video. The player brings up VATS, doesn't have enough ap to attack the mole rat torso, but somehow critically attacks the molerat torso, while at the same time being notified of insufficient ap on the HUD. This is clear evidence of possibly needing VATS to target and execute a critical on something.
It's clear in the case of the raider vaporization that there's no obvious targeting of a body part with VATS. However, there are other instances where it seems as though VATS was used even though the actual VATS targeting was never shown. For instance, at 1min55sec into the "Fallout 4 – Combat Gameplay Compilation" it's clear that the player possibly targeted the head of the raider with VATS, but no VATS targeting was shown.
While we can't necessarily rule out the return of "regular" criticals at this point, no one should be surprised if they end up needing VATS to execute critical attacks at some point.