Mist Walkers and Maiden vs. Poppy's Q (and possibly other abilities)

Both the mist walkers and maiden are only taking about half the damage they should from Poppy's Q. At first I thought it may be that they were only taking the %hp damage, but testing shows it's simply that they're taking only half as much damage as they should.

I didn't test other champion abilities, but I remember at some point before a single Yasuo Q wasn't killing them when an auto attack would (without crit). It could be the case with many other champion abilities, at least with physical damage.