Decouple gear progression from 4 mans (i.e., tomes), and you've solved this problem. Sure, people can get the drops from the 4 man dungeons, but only as a means to progress to 8 and 24 man content to get better/best gear (which have more DPS slots, hence lower Q times for DPS). Tomes would essentially go away. They're not needed.

SE can then provide really cool incentives for people who are geared to return to that content -- not chump-change gil. Mounts, unique glamours, crafting gear/recipes, etc. Basically, anything you can think of that's cool/worthwhile doing outside of gear progression throw into the pot of 'rewards'. And, ofc, you'd wanna do that content quickly so you'd likely Q as a tank or healer.

tlDR: No tomes for gear. More 8/24 man content for gear. Provide better rewards for those that are geared to do lower/repeatable content.