Warlords: Rushed out before it was ready, game was literally unplayable for days (weeks in high pop realms) unless you could play in the middle of the night. Raiding turned out okay (5/10), class balance was a fucking mess.
Legion: Again rushed out before it was done, class balance... well everyone could do everything but some specs were definitely miles ahead of others. Raiding was okay (6/10) from what I played but I quit after Helya.
BfA: Felt rushed out (again), I can't comment on raiding past the first tier as I only played for the first 1.5 months before I got bored and annoyed with the forced grinding...
Do I have any faith in Blizzard making Shadowlands good or allowing it the time it needs to be good at launch?
No, not even a smidge of hope. Shadowlands will be the first expansion I don't pre-order, I'll watch beta streams and follow that phase but unless I see clear changes from what we've had in Legion and BfA then I'll stick to Classic.
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That's also my fear, I can't understand why Blizzard insists on these endless grind models we've had in Legion and BfA. People are getting burned out from having to repeat content on easy mode (lower mythic + level than they can do) for efficiency, there are people in my guild who put their alt(s) on second and third accounts to they can multi-bot islands and dailies. How insane is that?