I get this issue too - to be honest I seem to be OK in FATEs in most places, but in Coerthas especially things are abominable. The mad rush of people overloads the game and I've been disconnected several times as a result of the PS3's sheer inability to keep up (FYI, the same FATEs work fine on my PC). The worst is the Svara FATE - since it's a multi-part FATE with lots of enemies everyone Zergs to it for the EXP, but it is just physically impossible to do on PS3.