Dungeon Roulette Bias

[MXMoondoggie]

I've seen this stated a few times and it never made any sense to me. Doesn't every dungeon need every role?

Certain dungeons are run less and need more roles filled than others which get groups easily. If you play Healer in roulette it seems like you get Toto-Rak a lot. Tanks often seem to get Aurum Vale.