This deck is all about Luminarch Ascension and dragging the game out until you can get to it. With 4 Ascensions and 2x[[Idyllic Tutor, you don't have to drag the game out for too long.
Best defense combo:
Palisade Giant
+ Indestructibility: Works very effectively against a lot of combos and with Negate in the deck you'll be able to counter a pretty substantial amount of exile.
The game plan is to basically just stall, stall, and stall some more. Safe passage and plenty of sturdy wall blocking will get you through enough rounds to get ascension going.
There's one
Council of the Absolute
in there in case you come across something scary or the other person has
Ratchet Bomb
. For that and other, similar purposes you have Disperse which is a great, versatile card for defense or offense.
My favorite counter that I don't get to use very often because Azorius really isn't my thing is
Render Silent
which is basically a turn waster. Your opponent really can't do much after you drop it.
Grand Abolisher is a fantastic stall card because it prevents your opponent from doing things to break through your walls like using removal or unblockable. As long as you have some blockers out, you'll basically have every other turn guaranteed on Luminarch.
Here are some higher budget options that I didn't include:
Greater Auramancy - Makes the indestructible giant combo that much harder to break (only thing that really can is beefy trample or infect). Also protects your Luminarch Ascension against removal or destruction.
Supreme Verdict - Stacks well with Indestructibility and is a great, reliable field clear.