Classes been tweaked significantly from Battlefield Bad Company 2. The Medic class has been merged with the Assault class and replaced by the Support class, who will specialize in heavy weapons. These will come with their own bi-pod attachments that can be rested on the ground and cover to deliver suppressive fire with high accuracy.
One of the biggest surprises is the news that there won’t be a Medic class in Battlefield 3. You’ll still be able to revive squad-mates in the middle of a fight, however, you’ll just have to do it as an Assault fighter. The Assault class can still deal plenty of damage, however, and the customizable load-out will give you alternatives if you’d rather run and gun than help fallen team mates.
In Bad Company 2, Medics could wield fearsome light machine guns. In Battlefield 3, heavy weapons will be even more devastating thanks to the destructibility of Battlefield 3′s environments and the addition of a new bi-pod attachment. If you enter aiming mode while prone or near a wall or windowsill you’ll deploy the bi-pod, giving your gun extra stability and improved accuracy while firing.
Heavy weapons are central to a brand new mechanic in Battlefield 3: suppression. Taking heavy fire will affect your ability to fight.
The Assault class carries a primary weapon consisting of an assault rifle — like the M16 and AK-74 — and is now merged with the medic class — the Assault class can now heal and revive teammates. It can also function as a more offensive class with ability to swap out the revive kit for a grenade launcher
The Support class returns to its role it had in Battlefield 2, with its main purpose to provide heavy fire from a Light Machine Gun (like an M249 SAW), and resupply teammates with ammunition. In Battlefield 3, the Support class is broadened with the ability top use lighter weapons and assault rifles like the M4, as well as C4 explosives.
The Engineer class in Battlefield 3 is very similar to the class in Bad Company 2: its primary role is to engage tanks and armored vehicles with an array of rocket launchers such as the RPG-7 and the SMAW, or use anti tank mines. The primary weapon is a carbine rifle, with a variety of unlocks available, ranging from shotguns to sub machine guns.
The Recon class carries a sniper rifle for long range engagement, but for Battlefield 3, the Recon class has a more active role as well. The Recon also has the ability to use a laser designator to mark targets.