The more I look at your images the clearer it is to me that the uneven bed is part of your problem:
The red boxes highlight areas where the nozzle was either too high above the bed, or too low. The arrows show parts of the skirt to the same effect - I guess there you can best see the difference in how strong the filament was squished onto the bed. My assumption would be that those parts warp where the nozzle was too high, the filament barely sticking to the bed and thus easily lifting off when getting cold. So, improving bed flatness or increasing the bed calibration pattern points seems to be needed here. That said, I never tried 11x11 with the dual extruder, it may be that it is not possible, but with the single extruder it certainly works and improved my prints (I have a bad bed also) considerably ( 11x11 calibration with heated bed possible? - heated bed or not in the end did not make much difference in my case). For the DX I get along good enough with the maximum pattern density selectable from the touchscreen (I think it is 7x7, but I may be wrong).
Btw. I in the meantime had a closer look on my bumpy bed ( Stumped and tired - #72 by Hauke ) - in my case I’m 99% sure that my uneven bed is the heated bed itself, not the platform below. And the bumps are such that shimming will not save me. I bought a new heated bed which looks much better, but yet had no time to install it and compare.
Still, as said before - never have seen such extreme warping before - is this happening for every brand of PLA you use? I have one spool of PLA that warps like hell, but all others I use are well behaved… If you buy all from the same brand, consider changing…