The addon shouldn't affect the combat log or WWS at all.
As far as the added health effects, I think that the addon checks against current health values on the health update hook, insuring that the players/member's max health value is constant, and then calculates the change in that value using combat log data <----- This could be totally wrong as I'm just a lowly user and don't pretend to truly understand how this works
I have invited Meloeth to register here and take part in the discussion. I'm sure he can answer your questions better than I.