This will be updated as more data comes in. Things known so far:
Aether: Playing with cliche decks. Expect phase shield stalls, TU rushes, and fractal. Firestall is a good call here, but be careful of devtal. Momentum + scorp is a cheap way to counter them. If it weren't for that play error, I think we would have beaten them. Discord is another good pick.
Air: Extremely versatile. Hardest pick to make
Darkness: Hardon for devtal. Expect quanta denial + vampirism, that's all they've got. Protect artifact and sanctuary are great picks, as is nightmare, but be careful what you use it on. If they're being sneaky, they'll use voodoll, but probably not on us. They'll be expecting reverse times.
Death: Poison stall is their strongest deck. The deck I thought would win the war for them was crusading arsenic. They can rush too. Anubii are musts.
Earth: Kakerlake is new to me. Can't call his moves yet.
Entropy: Will be playing discord with control and shitty attackers every deck. Play a creature-less deck and win. Play sanctuaries and win.
Fire: Has two decks. Weak creature rush, and bolt stall. Anubis + reverse time stops their creature rushes, which is why they'll stall vs. us every game. Either anubis or pharaoh are good calls.
Gravity: Really likes acceleration. Reverse time beats almost everything, GOTP beats their shield.
Life: playing with war 2 strategy. Expect grab-bow, firestall, and discord. Sanctuary and GOTP are great calls here.
Light: The element I'm most afraid of. HRmmm is an insane deck builder, we'll need to focus them. They can bring bolt-stalls up the whazoo, scorpion/nightmare is a needed deck here. Anubis + RT is also a good pick. They have durable hitters if they wish to rush, too. If we suspect dive, reverse time is needed, but they'll take bolt as easy wins versus us.
Time: The weakest team. I don't think they can pick a single deck I can't predict, card for card. Their veteran player, Gl1tch, is kind of a newbie with time, but he's used to being a stronger player, expect overconfidence from him. He has a habit of thinking his deck losses were flukes and picking the same ones again. He'll also think some decks are way better than they are, and want to play them everywhere. Good at strategy early war, way worse as it goes on.
Wadurrr: Pretty bad. They're unpredictable, but with too many duos to handle, they'll fizzle late game. They like bolt stalls a bit too much, but they can't rush for crap. RT stops nymphs if you smell them, but I doubt they'll nymph versus little ol' us. They're in the same "everyone thinks we're weak" boat we are, which means their teammates will be making play errors. A good team to throw the "I can't think of a deck" deck at.
Will get more serious as more data comes in.
