You might have noticed that I'm searching for ways to save old raids from being totally ignored. Last week I suggested that all raids be at the same gear level. This week: remove all epics from heroics and increase the abyss crystals needed for enchants.
Randoms would no longer be a source of any abyss crystals. The higher cost would mean that disenchanting in the highest tier raid could not supply enough materials. People would have to go down a tier.
Or would they?
Clearing old raids for shards wouldn't be a quick process. Despite gear advantages, some fights would need to be relearned. It could become so slow that abyss crystals wouldn't be worth the effort. The few that come from the highest one or two raids would be enough for the specifically awesome enchants like berserking. The 2 more stats from +10 stats to chest vs +8 wouldn't be worth the farming unless you're extremely determined to min-max.
This wouldn't be much help for restoring progression either, since the last thing a farming guild wants is someone who will use the gear.