@ Marv : there are deck I've used vs those league and had works quite good (IE at least 45/50% vs gold and 33% vs plat)
Gold : CCYB, RoL/hope, JMZ classic, tadabow tweaked, lava rush, the shutdown, I've GotP time, pestal, 500EM deckout.deck, and a personnal deck (the wyrm looks in duo deck if you want)
plat : RoL/hope, the shutdown, lava rush, I've GotP time, 500Em deckout.deck, big time bow woth a lot of variation, JMZ tweaked..
Those are JUST the decks I've tried. All gave me lot of money and score (I gained ~70k score since arena is on and play ~1h per day at best.. except two days where I played 10 hours). So i think there exist enough efficient deck to avoid a boring farm. and I don't even talk about deck available vs bronze/silver..