They have a trait in their Artifact weapon that heals for 18% total health after every Blink. I personally think that's pretty substantial. Out in the world, you can probably survive indefinitely unless you decide to pull some un cc-able mobs or something. Add this to the fact you'll probably always be using Shimmer apart from niche situations where Cold Snap may be of benefit, and you have a 36% maximum health heal at the get go, then 18% every 15 seconds. 2 charges is also flexible.