As a HEC pilot myself, it definitely has it's risks and rewards. It is a nice quick way of moving crews from tower to tower and exactly where they need to be. We try to minimise the amount of time they are actually on the line too. For example, keeping LZ's close to the work etc.
Any of the HEC accidents that have happened have all been pilot error. The Brim one, he ran out of fuel.
The linemen know the risks just as much as the pilots know the risks.
Skid transfer to the towers are probably more risky than putting the guys on with the line.