I don't see why they didn't just bring back a Dynamis type reset for Coil. Upon completion of a turn, you are locked out of that turn for 72 hours.

For Myth tomes they could do a trade in rate of like 1500 philos to reset weekly cap. (Sidebar: I'm not a huge fan of this one because it would increase some players' pressure to continue grinding but its better than nothing.)

They could also add a new currency called something like Duty Finder Points (DFP for short). A player would only qualify for DFP if they queue'd solo for DF (maybe even random dungeon queue). If random, when they get the acceptance message, instead of showing the dungeon name/picture, there's just a black screen with a question mark (to prevent players from withdrawing until they get the dungeon they want). The player receives DFP upon completion of the dungeon and can use the DFP to reset the Myth Cap (or whatever else you may or may not want to reset).

All of these ideas could keep players coming back to the game throughout the week. I think the thing that SE needs to realize is that Hardcore players are going to be just that. They "generally" (please don't flame if you consider yourself hardcore but also enjoy helping others) have no interest in carrying newer players through content so you might as well just let them aspire to be as hardcore as they want. Slowing them down is not the ideal way to secure long term subscriptions nor is it a good way to get them to participate in other content.