I have been a persistant git on this issue with SEGA and finally, after shooting down all the bullshit with counter points, this is what they have responded with:
Ticket #51384: DLC Achievements Not Unlocking Your request (#51384) has been updated:
Sean, Mar 13 12:14 (PDT): Hello James,
We have investigated this issue and due to various reasons a solution for this issue will not be available.
SEGA of America
So that's pretty much it with SEGA. I'm still working on a community driven solution to this.