Deco Lav vanity sink drain issue....?

I installed 2 Deco Lav vanity sinks. I finished it off with 2 Hansgrohe widespread faucets that included the drain assembly. The problem I have is the drain outlet flange is not sealing at all. Hansgrohe provides a gasket and does not require plumbers putty.

The only thing I think could be an issue is the drain hole has a slight contour around the edge possibly causing the leak. My question is if anybody has had problems with Dec Lav and would it be recommended to use their drain assembly. I figured Hansgrohe to have a higher end assembly but it does not work in this case.

PS: I used plumbers putty in place of the gasket and it leaked worse. Maybe I need a thicker gasket around the drain outlet flange???

In another location you say the "contour is at the rear" implying an assymetric design, but here you say it is "around the edge" implying symmetry, which would be a completely different issue than a "tear drop" shaped recess. WE would have to see the drain hole to determine WHY you are having the problem, since I have not had that problem even though I ALWAYS use plumber's putty, or the supplied gasket.