Not true IMHO - in High Lord Mhoram's time (and how many years did he have left to live anyway at the end of PTP?) the people of the land had health-sense and were capable of discerning evil. The thought of a Raver penetrating the Council would have been unbelievable at his time for that reason.
I agree - the New Lords had lore the Old Did not - the ability to meld minds together. Had Kevin's council had this ability, Foul's cover would have been blown early enough to let things get so out of hand that Kevin fell into despair.
With the New Lords, were a Raver even able to enter the council, likewise, his cover would be blown when this mindsharing were attempted.