Do DRIcore panels need to be flat?
In my opinion yes, you need to eliminate the dips. Anything that will be spanned over a low spot by the Dricore will move under foot. It is after all only a high grade OSB and the T&amp;G joints will eventually fail somewhere over time.

The whole floor does not have to be level, just on the same plane.

On a concrete floor, a laser level will drive you crazy, do not do that to yourself. Technically, it needs to be flat, ideally it should be level, but level is not critical. I see eyes rolling now.... A string line will give you a good idea of what is in plane, not relying on it needing to be level. I refer to a level as a straight edge only, not using the bubble to determine level. Usually a level is always straight, therefore a good candidate for checking flatness over a given area. It is a lot of "hands and knees work". Scoot the level all over the floor to see how the floor plane is in any 4 ft span. This will help locate the high spots. Situate the level or straight edge over 2 high spots, anything over a 1/16" needs shimmed.