Well, mostly true
I looked again and actually as far as I can tell Molten Core and BWL both don't have female bosses, but almost every boss in each of those instances uses the models of random trash mobs from the world rather than new models and most of them can't even talk.
Unless you count "Deathtalon Flamescale" as a female boss but I don't
You could call it "lazy sexism" if you really really wanted to but I think that'd be a stretch, it's clearly not something they are continuing to do either, as every multi-boss tier since has had plenty of women
Point, I missed that one too
Maybe one of the dogs is female? :P
I keep forgetting that while this is one tier it's still three instances
Terrace might be all men too, not sure if Lei Shi is meant to be a girl or a young boy