900k sounds like an impossible value that you got from... where? I'd love to see proof of this number being possible in arenas. Because you'd have to take like three times your health in damage within 5 seconds and survive it, but if you can survive that then why do you need death strike rofl.
Frost has a trait on the Artifact weapon that increases Death Strike healing by 100%/200%/300% per rank when Icebound Fortitude is active.
Essentially it is possible to go from 1% to 100% hp if you have 400% (Rank 3 + a Relic that gives you a rank) and a Dark Succor proc from killing something.
edit: Ah just realized you said arena... not sure to be honest there. It can only realistically be used twice every three minutes anyways since Death Strike costs 45 runic power to use once.
Edited by drzy, 06 September 2016 - 12:59 PM.