As much as I love the topic, I thought I should comment to clarify this bit (since I think it actually does make sense). I wrote a little about it here Changes to Faction Events - #10 by Jonathan
but essentially although the multipliers OR percentages may be the same across rarities, it’s never both, as the total will add up to a different static number for each rarity. E.g. Legendary rooms add up to 1.8, as in the example I gave there.
Edit: Rare = 1.35, Ultra-rare = 1.5, Epic = 1.65, Legendary = 1.8 (going up by 0.15 each time).