Decay should be in medium section because: I don't think anyone has reported this, but if you play a ROL, and decay has 8 aether quanta, then he fractals those, maybe cuz they have attack and don't cost anything. that is the only way to win decay, unless you get faced with too many pests.
At the start: Keep one ROL in your hand at all times, he has 2-4 siphon lifes in his hand usually. fractal your ROLs before Decay can play fractal (in case he siphon lifes a lot) try and keep ROLs on your field all the time for Decay to fractal them. even if he plays electrocutor , he usually has no aether quanta from fractalling every turn. You're safe once he fractals your ROLs once, unless he siphon lifes YOU to death. try and keep the ROLs there for a few turns and wait for him to use siphon lifes on them. Then put out dragons, light nymphs, archangels etc etc. Because he has a lot of dark quanta to spare and can drain a lot of life. Decay is so far the only FG I can beat because it does something it's not supposed to. If there are others, then this is the one most obvious.
Although I use this:
5lk 5lk 5lk 5lk 7jo 7jp 7jp 7jp 7jp 7jp 7jp 7jq 7jq 7kc 808 808 808 808 808 808 808 808 80e 80e 80e 80i 80i 80i 80i 80i
Light nymph helps against elctrocutors, ferox.
You can use this as well alternative to light nymph:
5lk 5lk 5lk 5lk 7jo 7jp 7jp 7jp 7jp 7jp 7jp 7jq 7jq 7ju 808 808 808 808 808 808 808 808 80e 80e 80e 80i 80i 80i 80i 80i
Although more vulnerable to poison, long term damage, without shards, I think it's much faster against most of the gods beatable.
I think the deck on first page has a slightly higher chance of winning but takes longer, but it really depends on what your playstyle is, if you want to win more, but take longer or if you want to have your win chances little lower, but more speed.