like you said the shotguns will always be an issue and the MTA team have done things to try to balance them out
they have reduced the damage on the stubby already.
there is also a time delay for the shotgun its called the reload cycle unfortuntly ppl tend to find ways to get around thinggs like that like crouch glitching, wepaon switchings and so on.
they also took out jumping with the stubby in 0.5 to try to balance it out aswell.
personally i think the weapons are fairly balanced it just a matter of playing a bit and trying different ways to defend against certain weapons
but don't worry the MTA always looks for better solutions and ways of doing things