Yeah, they almost definitely didn't have enough time to correct the whole thing throughout. They focused on the close ups, the most important parts, though. I really hate it when people use terms like "derp frames" on sequences with a ton a movement like this version of World Shaking.
Could it look better? Sure. Did they have the time to redraw a bunch of frames when these movies were probably rushed? Doubtful. Does it look good *in motion*? From what we've seen, yes.