I guess the problem is that you can't halve the duration to 1 per 0.5 seconds (2 per second) because you don't actually lose anything if you buy it for just 1 DR.
Just realizing now, if you were to define a bunch of separate DR, I guess they would drain away simultaneously?
http://www.mygurps.com/r_absorption.html?p=ir&v=0 lists heals HP as +40% not +80%. Were you thinking of it like a leveled trait so that each dmg stopped heals 2 HP?