MoP>BC>Legion>Wrath>Cata>WoD
I thought Legion started off very strongly and fizzled hard by the end. Three months into Legion I would have ranked it number one, but 7.2 and 7.3 were...less than good. It honestly felt like different teams made the two halves of Legion.
I'm also still very against some decisions they made in Legion, like ilvl scaling the world and the extraordinary reliance on time gating to lengthen lazy content (Looking firmly at you Broken Shore).
As far as story goes, it also started off strong and then petered out with numerous lore gaps or contradictions including:
The Sargerite Keystone can suddenly open a portal to anywhere but the Legion couldn't use it to get to Azeroth for reasons, turns out the Army of the Light is just one spaceship of draenei that the Legion inexplicably can't defeat with their seemingly limitless number of spaceships, the titan souls were captured by Sargeras even though they supposedly were in Azeroth's keepers, demons can't truly die on Argus ...but also can..?, Sargeras is hiding in a cloud y'all, everything to do with void elves.
If Legion was broken into first half and second half:
Legion(7.0-7.15 )>Mop>BC>Wrath>Cata>Legion(7.2-7.35)>WoD