Yes, mass balances help (and are often found on full sized airplanes)...most full sized airplanes use cables which have a lot of "slop" in them so the mass balance is really necessary.

Most model rely on the stiffness of the aileron/linkage/servo to dampen out vibrations. Why? Probably because it is simple to upgrade to really powerfull servos/linkage/etc. where it is harder to get pilots with more torque...

But typically 3D airplanes are built so lightly (so they can hover etc)...that they are not very stiff. I blew a couple of them up before I got it figured it out. But back then they were 40 sized.....
Steve