The Vostro 3550 comes entirely in matte, but the battery life is only normal, and the specifications are considered outdated already (you might want to wait for it to be refreshed if you are not buying in a hurry)
15.6"
Dell
Vostro 3550, i5-2450M + AMD HD6630M@RM2257, 4GB, 500GB(7200rpm), W7HB, backlit keyboard, colors: silver/ brown/red
Vostro 3550, i7-2640M + AMD HD6630M@RM2920, 4GB, 500GB(7200rpm), W7HB, backlit keyboard, colors: silver/ brown/red
*use remaining money for warranty extension to 3 years

Other than that, you're going to have to make compromises on the non-reflective screen unfortunately
15"
Asus N56Vz-S3088V, i5-3210M + Nvidia GT650M@RM2699[Bang&Olufsen], 4GB, 750GB, W7HP, subwoofer and backpack

Toshiba Satellite L850-1001X, i5-2450M + AMD HD7670M@RM2499[2.41kg], 4GB, 640GB, W7HP, 3 years warranty

These two are running on an i5 processor, which will help save you some battery life, just try not to expect too much from them since almost all laptops within your budget only come with 6-cell batteries

Can try these:

Acer
[Ultrabook] M5-481TG-53316G12, i5-3317U + Nvidia GT640M LE (28nm Kepler) + 128GB SSD@RM2899, 6GB, W7HP

1. The GT640M should be able to handle Diablo 3 smoothly, no problems there
2. If the built in battery dies, then you're going to have to replace with a new one... batteries are rather susceptible to heat, which is going to be a problem here for the Acer M5

Based on the gaming benchmarks here: http://www.notebookcheck.net/Computer-Game...ds.13849.0.html
Both GPU would be able to handle Diablo 3 at maxed settings (presumably at 1366x768)

Batteries are usually around RM200-300? Its hard to say, you might wanna check with Acer for better feedbacks

Its Kepler-based, so no worries there