I was angling for this: (and I may need to spell it out better in the fic)
The damage Deathstroke (coupled with whatever his body was doing after the youth sucking machine) was immediate and permanent - like it killed off heart cells, so there was no chance to recover from the damage. That added additional stress onto the living cells, which broke them down too.
Also, plot gods?
Actually it is the plot gods concept and of course your excellent story telling that has kept me in this thing rather than just dropping our due to my reservations about your story premise. I keep thinking I will just stop then the next chapter comes, I read it, and get back hooked again.
Your true evilness is spinning a good tale, even one I really don't want to read.
Mike
Well, I'll take that as the highest compliment! 
