I've been leveling SAM and I feel your pain.

The issue with setting it up as you suggest is that 51-59 and 61-69 are all part of leveling. Part of the reason leveling pops so fast for 60+ DPSers is because so many people grind out SB dungeons, removing that from leveling roulette wouldn't help overall, it would just make a new roulette that people run more frequently.

I would be in favor of separating 50 and 60 roulettes though, while at a glance this might seem like making longer queues I think it would help overall. Once I got past 63 I stopped doing this on my healers because on the off chance I got a level 50 dungeon it was basically no exp.

But yeah at the end of the day grind out some beast tribe quests or hunts, at least then you're still being productive. Or Netflix.