Right now after these nerfs I feel rainbows are less consistent than some of the new ideas. And it does not matter how many decks there are outdated, as long as there are 1.21 decks too (and I see a number of 1.21 non-rainbow decks there).
Ok, just play a non-rainbow deck with draw (time aether?) or with healing (fractal + bonds?). I guess these decks can be consistent enough.
I'd recommend
my anti-FG (http://elementscommunity.org/forum/index.php/topic,4958.msg55301#msg55301) deck, because I feel it's pretty consistent and can beat all FG (though some like obliterator are still quite hard), but it's half time half rainbow, and somehow some people claim to have much worse results than I have... strangely enough I managed to upgrade ~10 cards with it (since the beginning of 1.21), so what I started with was even less upgraded.
And about those outdated decks... some of them have been either updated a few times since then, or you can find more up to date versions in posts at the end of these threads... generally if there is still discussion in these threads it means that at least some version of that deck is still useful in 1.21, maybe with some tweaks probably already mentioned in that thread...
And my own thread is quite outdated even though I created it a few days ago, because I added a few cards, removed a few and upgraded quite a lot
It's also faster than the original... I'll have to update it at some point, but right now I only update the deck itself.
yaladilae's variant (http://elementscommunity.org/forum/index.php/topic,4958.msg56381#msg56381) is also very good