Shard store doesn't help unless you're getting shards of toons you already have maxed. And if you're buying shards of toons you have maxed, you're doing it wrong.
That being said - I'm not sure I buy into the silencer hype. Putting off Hera and Ezra to farm KRU not only hurts both ghost and phantom ships, but it hamstrings you for Thrawn and Palpatine.
Don't get me wrong - silencer is a hard hitter, fast, and relatively easily gotten. But you have to be aware what you're sacrificing to farm a ship that isn't strictly necessary. I went after it, and now it doesn't even make reinforcements.
