I haven't seen a dragon yet in game, but I assume this is because of the unit scaling? I'm not a big fan of the scaling option, but it looks like perhaps the scale factor needs to be adjusted for large creatures.

I wish there was an option to just leave the units their tiny normal size until we zoomed out to the cloth map for the switch to the statues. No matter what scaling option I select, I find the effect very off putting, even with scaling off, everyone stays 40 feet tall.