After reading this thread I decided to make the Whispers of Silence a much more useful item and better balanced for BG2:EE. The original function of the cloak is a bit misleading because of how the opcode works and it rarely protects you from anything at all. This mod will make the cloak protect you from all illusion removing spells including True Seeing, Oracle, and Detect Illusions. It will still be beaten by a thief's Detect Illusions skill but I could change that if I so choose.
To install just extract all the contents of the zipped folder into your game's directory (the same one with the chitin.key file) and run the setup-ImprovedNonDetectionCloak.exe file. From there just follow the on screen instructions.
This mod was designed for BG2:EE but should work in BG1:EE just as well, only you won't likely notice the impact of the mod since almost no one dispels illusions in that game.