Short version. I'm not a "Players have to have 80 health or I won't consider them" kind of guy. Yet, on my 5 BL teams, I'm split almost completely down the middle with 78 over 80 and 79 under 80.
Just using those numbers and kscho's 20%, 15.6 of my over 80 health players would be on the DL while 63.2 of my under 80 players would have to populate the rest of a world's DL.
I bet I could find teams that only have 1-2 players under 80 health. If I had to guess, I'd estimate that 600 out of 800 BL players in every world have 80 health or better.