Hm, don't the more powerful blasts of lighting shown the victims skeleton? Did so with Mace and Anakin, so that could imply that he turned up the volume. But anyway, ya regardless Vader survived from the throne room all the way down to the hanger bay on a moon sized battle station.
Vader survivng that blast shows how strong he really is and that he isn't really weak to Lightning. Then to have to make his way from the throne room to the hangar bay shows his incredible fortitude.