Help Understand Low-level Roulette

[Amelia_Pond_Behemoth]

When you're level 50 you can be matched into any dungeon, so the pool of options is wider. When you're lower level, there will be dungeons you can't run because you aren't high enough level, so less options.

That still doesn't explain why TC was level 49 and had an average wait time of over 30 minutes.