I can honestly say that I am not a fan of the skill combinations....the one that quickly comes to mind is this whole perception thing. Ok so Spot and Listen could be combined into a percption roll since they are passive acts however searching is an active attempt to find something...One can accidently overhear something but when you attempt to listen in your are activly doing something so it is best that there be two 'Perception Rolls'
an Active and a Passive.
Also the comment about Investigate being irrelevant is something I hnestly believe is an erronous statement.