I tested priest/druid some more today and we encountered several issues we already observed earlier with Chain of Life.
The transferred dmg seems to be not always 15%, but more, seen in this scene where all dmg the tank got were whitehits form Nayat, last one with 525k, resulting in 139k transferred dmg, which clearly is more than 15%, but about 26%.
https://gyazo.com/125e2c7a793bfa65cc30da787d4499c3
Also the chain does not immediately break once the caster falls below 30%, if you are below that threshold for only a brief moment, nothing happens.
I guess the worst issue is what happens when the target/tank recieves dmg from multiple sources in a short time, then not every received hit is not only stacked together into one big one for the caster, but also seems to add up by wrong calculation, seen here during Jerath event:
https://gyazo.com/60a31ef0f874728b8917b469515f3074
The tanks hp did not even flinch that much, however I got a huge dmg spike of ~1,38kk dmg, if this were 15% of the tanks recieved dmg...well, do the math urself.
I guess the first issue also has its effect here.
https://gyazo.com/e3347c4894bc45b4271b134290655d6f
So clearly something is still severely wrong with Chain of Life.
Cheers!