dobies without the cropped ears sure can look like rotties & vice versa!
My brother's female rottie looks just like your dobie!! People used to try to tell him he really got a dobie instead, but there's no way that happened - my female is out of the exact same parents as his female (and all our rotties combined came from my DH's parents' 20 year long rottie kennel), just an earlier litter, and it's funny how much they DON'T look alike for having the same parents!