See thats the thing though, it reduces HEALING...
As a M:TG player differentiating terms can be the difference in winning the game.
I believe that the lifegain from FF is unaffected by GW. I would say this needs testing but I could have sworn I read about it somewhere.
Similarly, but ona smaller level, dorans blade would also no be affected by GW.
Its flat life gain.
Even after all this, GW still is not going to shut down an FF jungler at level 18 with 3-4 items while youre at 15 with 2-3 items.
Remember most FF'ers get FF then go tank, thats to be considered too if youre thinking about how to beat them.
While I really like Thornmail's idea, I just absolutely hate seeing it on an enemy champ, it literally means I have to ignore that guy til very last and only with at least 2 more allies around.