I'm also using 3.5G (which is, in fact, HSPA+ (HSDPA, HSUPA, if You filter out stupid marketing names), without such problems.

First of all, it's plain bullsh*t that it's device fault. Most likely, You just got bad ping due to route between Your device and MMO game server. Other choice is bad quality of service from Your operator.

Follow Hoga advices, to filter out possible cases.

/Estel