I don't know about you, but sitting around an environment waiting for 5 minutes at a time just for the enemy to have a CHANCE of spawning is a complete bore and sucks the fun out of the "Hunt" for these enemies. I was waiting in The Gulch for about 35 minutes for [b]F[/b]uckface McGee to spawn only to get two generic Cabal HVTs and a Fallen one. The ones tucked in the Lost Sectors are great because they're guaranteed to be there and it gives a new reason to do Lost Sectors again. So to fix this; Maybe increase the frequency of Wanted Enemies spawning instead of the generic High Value Targets, and possibly add a different text box that says "A WANTED Enemy is Nearby" instead of saying "A High-Value Target is Nearby".
I notice they spawn around the time when a PE is about to take place, if that helps