I think you see more ice ladies because they are so easy to kill, and drop urns very easily. I snagged two just doing quests or going there randomly while selki hunting.
As for bloody cubes, I haven't killed as many as I have ice ladies, but still haven't noticed a drop in killing about 40 of them. That's not many at all, but they're a pain in the arse to kill so beside quests and a few I see here and there, I won't kill 'em. :/