The Sustains are individually stronger than anything most scrapper defense sets get (outside t9), but of course there is only the one power, and part of the stronger is the crazy good recovery.
For /Energy its a more better(tm) version of energize, with a nice heal, a Regen bonus and a 119% end cost reduction. That is easy to perm.
But basically they are some increase in survivability plus no more End issues in one pick.