This entire mess is retarded, and I think it'll hurt EA more than it will Valve. I will agree that Valve's restriction is somewhat draconian (since no other DD insists on it), yet EA is the one choosing to NOT make its DLC available on Steam, insisting on selling it solely through Origin and getting the full 100% of profit, thereby falling foul of Steam's provision.
Neither side is blameless, but in the end the customer is getting fucked in this entire equation, as is usual with EA.
I'll find some other way to purchase ME3, and no other EA game interests me anyways.
Creston