How to deal with frag rounds
Here are some recommendations to combat the dreaded frag-rounds:
Spread out! Splash damage can easily wipe out an entire squad - which includes your medics. Obviously if all of your medics are down, no one will get revived.
Use a VOIP system to communicate with your teammates. Voice communication will always be faster than typing your current situation or where your opponent is. The faster your team knows where the opponent(s) with the frag-grounds is/are located, the faster the target(s) can be suppressed and eliminated [in theory]. In my experience this also helps to notify the medic(s) around you, to let them you your location if you need a medic pack or a revive. You can use any VOIP systems such as: Teamspeak, Ventrilo, BF3 VOIP built into the browser, etc. If you don't know anyone in the server, don't worry. Most servers are clan based and looking to expand. Therefore, they will most likely post their VOIP server address.
Try not to repeat your paths toward the enemy. If you never switch up your approach when charging the enemy, they won't bother to nuke anywhere else. I know on metro this can be limited, but there are some paths less traveled: From US spawn from B to A, try taking the exit on the left and try to flank. From what I have seen, a well executed flank can turn the tide of the battle at any point with this method [ as most players sit on the far right to middle entrances of the metro[facing towards A] A different example would be from A to B [being on RU] to blitz the locker room on the left side. If you can hold locker room, it provides a great flank against your opponent(s). There are many tactical approaches to attacking / defending in every map - not enough time to post them all.
Use Smoke! It really does work! If you blind your opponent(s), then will only have a general idea of where to fire for splash damage. Smoke can provide the perfect cover to get the needed vantage &/ flanking positions.
Play on a server that restricts frag rounds. This is self explanatory, but a debatable option as DICE can technically justify you as a stats padder by not playing with the default restrictions on a ranked server. If DICE thinks you are stats padding, they can reset your stats to 0s.
Strafe. Keep moving and try to stay away from walls when its possible. A moving target is harder to hit - especially with the latest patch [see below]
Switch it up. Play a different kit that can help the players blitzing and in danger of the splash damage. IE: Snipe! At longer distances (if applicable) , you will have the advantage over frag rounds.
Also note, with the latest patch that just came out, DICE nerfed the splash damage and power with the frag-rounds to make them more balanced. It is now a lot harder to get that splash damage kill.