Well you will have to make a decision, do you want exp for your level 50 or do you want tomes for your level 60. Both doesn't work and I don't think it should be that way, it's just like regular life, you can't just have it all. However I think SE could implement a little box that asks you before you queue, do you want exp or tomes, after you made your decision you could be running it as your level 50 and get the tomes if you chose to do that, but can't get at the end the full or any exp. That would give us the option to run certain dungeons with different jobs, for example when working on a different relic and still getting the tomes without having to run these dungeons more than once.