You obviously don't know how the batteries work. Of course 2300 is more than half of 3000. 2300/3000 = ~77% the size. The problem is that batteries don't discharge at a linear rate. The more discharged a battery is the faster it discharges. If you pay attention you will notice that 100%-50% lasts longer than 50%-0%. 100%-99% is much longer than 1%-0%. So, with a smaller battery the rate of discharge will increase faster than it would with a larger battery. It might not be exactly half but it's closer to half than 77%.
I don't have a Nexus 4 but the user reviews seem to match with your description. That is the problem. The Nexus 5 only has 200mAh more battery but it has a 5" 1920x1080 screen instead of the 4.7" 1280x768 screen of the Nexus 4. The Nexus 5's Snapdragon 800 is better than the Nexus 4's S4 Pro for battery life and KitKat might have some battery life optimizations but the screen causes the most power usage on any phone. I'm not expecting the battery life to be much better than the Nexus 4.
The Snapdragon 800 power efficiency is stressed too often. If your screen is off and your phone is in your pocket, you will get great idle time. The issue with Android right now is wakelocks, and if the OS, apps, and hardware are setup properly, idle times should be great. Look how long an iPhone can idle for as an example.
The Nexus 4's battery issues were plagued by the msm_hsic wakelocks which came from the hardware design. If that gets addressed in the Nexus 5, I'd be willing to bet the battery will skyrocket. Remember, battery life is a domino effect in Android. Syncs for example typically happen opportunistically, so when the phone wakes up, a sync might try to take advantage of that wake time by the radio and perform the sync. So the more you have the phone waking up, the more it will sync. This sorta explains why my Google+ can sync for 5 minutes a day when I get like 2 posts a day in my news feed.
The funny thing is on the past few phones I've used, the Moto Milestone/Droid, Nexus One, Nexus S, GS2, I've felt that they're barely enough to get through the day. Interestingly enough, almost 4 years later, I'm still facing the same issues on my Nexus 4. And even then I swear I used my Motorola Milestone/Droid with similar usage patterns.