Question on trait effects stacking
I haven’t actually tried it myself but you could try equipping them 1 by 1 and doing some damage on a test dummy. Record the damage and then equip the next one and see if your damage is roughly the same or higher.
I tested Empowered Illusions and Phantasmal Strength on 2012.09.20. They stacked then, so it’s quite likely they stack now. I have not tested functionality of Compounding Power at all, so no idea there.