On further thought, a partial dust refund of the Classic Set may make sense here.
Say we use these numbers:
| Common | Rare | Epic | Legendary | |
|---|---|---|---|---|
| Regular Refund Per Card | 5 | 10 | 50 | 200 |
| Golden Refund Per Card | 10 | 20 | 100 | 400 |
You’d get dust for each Classic card up to the maximum you can put into a deck (2 C, R, E | 1 Legendary) priortising Golden copies owned (like regular HoF rotation).
A player with a full Golden Classic set would get 25040 dust, while a player that has most of the regular collection + some goldens would be looking at 8000-12000 dust.
In all cases you get the dust and keep your cards, like a regular HoF rotation.
Here’s a Google Sheet where you can play with the numbers here:
https://docs.google.com/spreadsheets/d/1PcpW6UER3IetpTMDxNYuUa6MC9e0k7KivpKBNGxUt-8/edit?usp=sharing
Make a copy, grab your total numbers from HSReplay collection and count the golden copies you have of each rarity.
I only see this as being a one-off with the rotation of the Classic + Basic Set to Legacy, so next Core rotation in 2022 wouldn’t bring with it any extra dust benefits.