One-time acquisition RNG for Patterns is completely fair IMO. Destiny isn't a game where completely deterministic loot is ever going to happen, and Shaped weapons offer enhanced perks so they are always worth chasing. I think there should be a way for non-Resonance drops to increase the chance of getting one, however - similar to the RNG protection on some raid exotics.

But in general yeah, there's plenty of room for improvement on the grind and how that fits into everything. The main "use other weapons to keep using the one you want to use" approach to things is going to overstay its welcome fast. I'd like the materials to come from other sources, like from leveling Shaped weapons so they can consistently reward Reshaping themselves.