regarding Split the Soul:
In the tooltip it says you get 25% dodge incorporeal and concealment (but it is not telling you if it is stacking or not)
But the buff in the buff bar tells you 50% for dodge incorporeal and concealment.
So either the tooltip is wrong or the buff description because they contradict each other.
What it actually does...
It provides 50% stacking dodge capped at 95% which seems to be fully functional.
The 50% concealment stacks with lesser displacement (25%) and Smoke Screen (20%) and displays 75% and 70% which seems to be correct if it is intended that it stacks.
But Split the Soul does not stack with buffs (tested Displacement and Blur) which is strange.
The 50% incorporeal does work but it does not stack with a ghostly item (it still gives you only the 50% from Split the Soul) and the question is if this is WAI?
an obvious bug is that the 25% incorporeal from the Shadow Veil enhancement overwrites the 50% incorporeal from Split the Soul and you have only 25% no matter if you buff Shadow Veil before or after activating Split the Soul.
All this is displayed in the + tab in the character sheet at avoidance defense, the question is of course if this is only a display bug but it is obviously at least such a display bug!