The movie sucked. Not only the power scaling and misdisplay of the damage their power should be doing but the fact that Toriyama seemed to forget key importance in the movie. First, Frieza was revived in pieces from when Trunks cut him to pieces and destroyed them. We see the dragon balls bring people back as a whole, Cell shot Trunks with a ki blast yet he wasn't revived with a hole in his chest. There's people who were blown up by cell, androids, Majin Vegeta, and Buu yet they all got their bodies back. Toriyama forgot that Dende made his dragon with the ability to grant 2 wishes so Frieza would have been brought back as a whole and wish for immortality.
Another misconception. The dragon does bring people back to life even if they were brought back before. Goku couldn't be wished back with Dende's dragon balls but everyone else that were killed were, they wished everyone that was killed back more than once and I highly doubt it was always new sets of people (Cell and Majin Vegeta); the Namekian dragon balls brought everyone Buu killed back and we know it can bring back people who died before but it use to only bring 1 person back at a time now it can bring back everyone at once, a big powerup for that dragon (I know it was made by the new elder but Dende made a stronger set of dragon balls than Kami and its power didn't jump that big).