However, I'll steal this moment to talk about an idea Kolyarut brought up on Twitter:

What if the Archeology keystones that made Heroics easier were permanent? As in, you use the keystone for a dungeon once, and then you're able to activate the relic during all following visits without requiring more. Keystones would essentially become "dungeon glyphs", and there would always be demand for more due to alts.

The purpose of keystones could be retuned from minor buffs to reducing the difficulty of the dungeon significantly. Think of going from Stonecore difficulty to Hour of Twilight difficulty. Activating the relic could remove a mob or two from trash packs and disable/negate one key ability from each boss.

So Heroics would be Heroic at the beginning of the expansion, and as relic activation becomes more common, the difficulty would drop faster. Also, people who wish to play dungeons with the higher difficulty could simply choose to not activate the relic (although nobody should expect this in Dungeon Finder). And finally, many of the optional dungeon achievements could be tied to the higher difficulty, like surviving a near-wipe ability that's normally disabled when the relic is activated.