I saw LP, Metallica and the Offspring last year at Rock im Park, and I was able to see all of them because each played on a different day.
I think Soundwave has too many bands on too many stages. Too many bands overlapping. All the stages even finish at the same time. I know it's not a full blown festival but it should be one. So most of the big bands are on Stage 1 and 2. And tons of other small bands on 4 other stages. Who's going to watch all those when most people come for the headliners?