Can you clarify? "Backcountry" to me makes me think skiing... are you talking remote ice climbs? Like what do we carry for something like Drool of the Beast?
Gonna assume remote ice climbs and answer anyways:
1) Pre-hydrate. I only carry 1 32 oz bottle for a full day of ice climbing. I compensate by hydrating like a fool the night before. Normally I drink a 32oz bottle around dinner time (interspersed with beer or wine), then go to bed with a full Nalgene on the nightstand. I'll need to get up 2-3 times to urinate, at which points I'll drink about 1/3 of the Nalgene. The goal is for it to be empty by morning. Then I drink 1 more 32oz bottle on the way to the trail-head. So climbing with only 1 32 oz bottle for a full 8-10 hour day is quite reasonable if you start off that hydrated... Even with a triple Americano to start the day I'm peeing crystal clear...
2) Clothing... only piece of clothing in my ice pack is my puffy and a warmer pair of gloves for end of day...
3) Screws: switching to almost all 13cm's this season with a few longer ones for belays...
4) Biner's, except for a few lockers all super light wiregates... Petzl Ange S & L's
5) Slings: I'll take flak but lots of dyneema alpine draws... only a couple double length nylon slings...
6) Less Screamers.... used to carry lots... now only 2... lead falls on ice in 10+ years = zero (knock on wood), so felt like I was being a bit too paranoid... now I only use screamers on the first couple screws...
7) Rope... 9.4 is the fattest rope I want to ice climb on, except for TR. Prefer leading on 9.1 or 9.2 if it is a pure ice route...

Backpack... Wild Things Ice Sack or similiar CCW... light & simple....
All I can think of for now... but basically when I am racked up my backpack weighs less than 6 pounds (first aid kit, water bottle, belay jacket, yummy food).