From Dark and Darker Wiki
I think the opposite. Part of what makes IM's stat system so good is that all stats have pros and cons. No stat is "just better," nor is it supposed to be.
Yes, true magic damage ignores the headshot multiplier, but it also ignores limb multipliers, so you get full damage on limb shots. Also, you're almost never getting the full 1.5x on headshots anyway because pretty much everyone is going to be wearing headgear (or using the lizard/lycan skin, but those also come with built-in HDR).
More importantly, because it ignores magic resistance, it's better *when you most need it to be better.* Like when you're fighting an iron will barb.