Mass Effect's PC DLC problems seem to have been solved, even if you might end up spending a little more than you might like to get hold of every bit of content.
The series has some truly excellent DLC. Playing the games without them certainly hurts the experience as you miss out on some killer stories. Mass Effect 2's Lair of the Shadowbroker and 3's Citadel come to mind. Up until now, though, getting them on PC was quite hard as the DLC wasn't sold on Steam or Origin specifically.
That has now changed though as you can now buy bundles containing the DLC on the Origin store. Sadly though, you can't pick each DLC up individually, and they are also pretty pricey. The Mass Effect 2 DLC bundle is priced at $24.99 and Mass Effect 3's is $29.99.
Hopefully, in time they might come to subscription service Origin Access or go on sale for dirt cheap so PC players can get their collections together. If you can't wait, though, have at it.