I've always imagined that the devastation and pain brought on by Force lightning was determined by who's controlling it. For example, Sidious was torturing Luke in Episode VI, kind of playing with his food before he eats it, so he was allowing Luke to live. When he blasts Yoda with it 20 or so years previously, however, he intentionally wants to catch him off guard and knock the "arrogant" little sucker right off his feet, but not necessarily torture him into submission (probably because Yoda would eventually blast him backwards). When Sidious electrocutes Mace, that's the death blast, what you really get when Sidious wants to kill you. That was especially horrific (especially for Star Wars) because when he has his hands chopped off the audience kind of says, "Oh man, he's dead, no absorbing it this time." One of the best scenes.
As far as lightsaber combat though I think Mace had Sidious owned, but as soon as Anakin shows up Sidious know he's fine.