The Battlefield Blog has an update on some of what DICE has learned through the Battlefield 4 Community Test Environment they've been using to experiment on the latest installment in the shooter series. This includes more on improving the game's "netcode" (their quotation marks) as well as an initiative to examine core gameplay principles. Here's part:

Improving Netcode
Making improvements to the “Netcode” in Battlefield 4 has been a top priority for us. Some of the items we’ve been specifically looking at is how to decrease the feeling of getting killed when behind cover and getting killed without initially seeing a damage indicator. The improvements we did were released in June, and we’re looking at testing out additional fixes during the coming months.

Core Gameplay
The core gameplay initiative has started, and in the first phase, we’re looking at making improvements and fixes related to the new Dragon’s Teeth expansion pack. One of the main items that we wanted to test was the all-new Ballistics Shield, and based on the feedback that we received we made the following changes that’ll make it for the release of Dragon’s Teeth:

• Shield bash damage has been tweaked, it is no longer possible to one-hit kill enemies. The Ballistics shield now better matches with the initial design intent
• Single tank AP-rounds now kill those carrying the Ballistics Shield, something that previously wasn’t possible.