In most games like these, characters that start out being available only through purchase eventually become farmable (usually when new pay only characters are introduced). I've bought a few chromium packs and I can't complain about the drops, but without the stars characters aren't useable. The "in for a penny, in for a pound" aspect is disheartening.
TLDR: Will pay only characters ever be able to be farmed? (Maybe the new shard shop?)