Well... yeah, of course your level 70 rotation doesn't fully develop (on most jobs) until level 70. But it's still useful to know what pieces you're working with and how everything fits together along the way. It's a lot easier to fit in something new if you already know how everything you had works, than to just jump to the end and figure everything out all at once.

The solution here seems absurdly simple. If you want to do at-level content, queue for it. Roulettes aren't for that; their bonus is just to help all the players queuing for specific instances. If you're queuing for an instance on par, you're still getting relevant experience.

Personally, I found leveling with roulettes to be less than ideal, mostly due to missing out on any relevant dungeon loot. I'd rather queue for the same dungeon over and over, still getting decent experience, and also the chance at gear upgrades.