Thinking about this suggest. I agree with Meer that Grading is fine.
I think increasing the special ore rates would be a solution, for example Enriched Etherium/Enriched Etherdeocon at +9 to +10 gives us a 25% chance (compared to 18% base ores). This chance is not very impactful, to the point its not really worth using these ores unless you can donate, or have extra laying around from daily rewards.
I think Increasing the chance to 30% at least at +9 to +10 would make a large difference, however this solution also hurts when Muh Coins feel hard to farm. I can get around 200-300 a day from main office boards (using 3 accounts at the same time, this take roughly an hour), but not all players can use that advantage of multiple accounts. On average I get about 50 from events per day, and 10 Guaranteed from Daily Login. The only other available coins are from Riddler, which is at least 75 coins per day, for those that do it.
Using 1 account (no alts) you can make 60-100 + 50 + 10 + 75 Coins per day. 195-235, which is 4/5 days for a box, 1 hour everyday of farming for coins, and anywhere from 15-45 minutes of Riddler everyday depending on your RNG.
tldr: Gimme more Muh Coins, and increase the +9 to +10 refine with special ores from 25% to 30%