Make non-rage characters involuntarily HF whenever a real combat (non-sparring) attack has been landed in the radius of 15 tiles. The spell can not be interrupted by any means except teleporting character specifically clicking the "cancel" button, in which case the character "Faints from fear" - loses all SHP and drops unconscious instantly.
Or, better yet, remove the Nonrage Immunity and make the above a skill like "Pacification" which is mutually exclusive with Rage.
There. You wanted to be an immune to death non-PvPing sheep? You are now one. You can either try and teleport or lie down and hope your PvPing friends win to participate in the looting (or wait until the combat moves aside a bit, get up and run away).