Is this intentional? If so how much rarer than epics chests are they?
Do you mean as PvP bonus reward chests?
Yes. Also is it possible to get three epic chests for pvp rewards? Or is it only possible to get one at a time? And are they a percent chance based to get one or on a rotation?
Legendary chests aren’t currently obtainable from PvP bonus chests. This was mentioned in this other thread and is a bug with the display. Epic chests only appear in the last slot, and to prevent bad luck, everyone gets the same number of Rare and Epic chests over a set number of chests opened.