Which older DLC are worth the purchase?

I stepped away from MW5: Mercs just after I finished the Kestrel Lancers DLC. I ended up back into the HBS:Battletech until MW5: Clans got me back into the seat :). When SOK dropped for Mercs I picked it up and have been having a blast... well except for the Raid missions with endless light clan mechs that I've now learned to just avoid.

I'm considering doing another play through and I'm wondering if any of these DLC's offer enough to add to the collection now, or just wait for the next sale?

Call to Arms
Rise of Rasalhague
The Dragon's Gambit
Solaris Showdown

Or is the Kestrel Lancers, Heroes of IS and SOK plenty.

Love to hear your opinions, the reviewed are mixed on steam hence looking for more input from the reddit scene.