But I would perhaps dissuade cabals from using Tremblefist if enemies are showing up to retrieve against pk opposition.

For example, a hero could come with lowbies and tank for at least a little. Even if the hero bails, at least he took the risk of showing up.

I like Tremblefist as a foil against those guys who repeatedly try to gank but won't solo retrieve attempt Vs any opponent. They send in the lowbies when faced with a fairly even fight. And I'd like to see even fights encouraged, not reward avoiding them.