Team Bisset said:it has been on sale once when i picked it up like a year ago been ages
Dark Forest pack was on sale back in July of '11. Other than that, no, it doesn't look like the DLC has been on sale ever. This pack is, iirc, offline. It only takes like 5-10 minutes to do though. It's a really pointless DLC.
The Trials of St. Lucia though, that's another case entirely. A horrible, horrible piece of DLC. If you are thinking about doing it, I would do it sooner rather than later. It is, after all, an almost 3 year old game. I wouldn't expect EA to keep those servers up very much longer. And yes, Unfcnbleevibl has the right of it. The trials are long, boring, and grossly overpowered against the player.