Faction guide with list of vendors that supervillains can use along with helpful information on how to emulate the whiteknights:
http://wiki.project1999.com/An_Iksar...Through_Murder
I vaguely recall reading somewhere that the mob reaction delay is intentional so that the player has a chance to avoid new spawns and safely traverse the range of mobs which con Threateningly. Other factors can affect this; if you're sitting when the mob spawns or if there is a social mob already engaged when it spawns, the new spawn instantly attacks rather than the 'play dumb' behavior that a single mob will display for something like three seconds.