If you do a search on this forum, you'll see a couple of people (not many) have this issue. For the first 1-3 days, usage is great at a standby rate of 3-4% PER DAY, and then for some unknown reason, it suddenly changes to 3-4% PER HOUR.
I'm one of those unlucky few, and I just finished up a conversation with ASUS support on this very topic. Their first step was to do a factory reset. Next, I was told to drain the battery to 1-2% and then charge fully (and avoid overcharging). When that didn't work, they generated an RMA number for me, and that's where I'm currently at. They didn't even ask me - they just said they'd generate an RMA, so I'd say they consider this abnormal and warrantable behaviour.
So your best bet is to exchange if you're within your return period or request an RMA if you're past that.