I tried to check how much is healed by the calculator bot ally passive benefit as its definitely a tank ally. I was surprised to see I got healed 800 from a 2400 dmg. I thought it was too big so I waited for it to trigger again but nope it did not. Only time it gets triggered is on the first hit. I guess it was too good to be true. Please fix this. Thanks!
It's not proc'd by taking damage. It basically just gives you a heal every time it's off cooldown (20s I think) as long as you're still in combat. I went and tanked one of the flashpoint general pairs to test it and I was getting a 16K heal pretty regularly.
What Illumin said, the passive has a 20 second cooldown and the strength of the heal is based on your Health stat.
I just tested it. I maxed out health and put the refractor in and that bumped the heal up to 17,900 from 16,300. So yeah, it's health based.