This is typically a job for the motor controller rather than ros_controls. Increasing torque is not always as easy as upping your set point (by increasing the angular velocity component of the twist), as you need to tune the motor controller directly. Typically there is a PID regulator which regulates the current sent to the motors - this needs to increase more quickly to be able to cope with course ground. Increasing more quickly also means more sensitivity to noise, and you can get problems with vibrations.

For skid steer robots, the outer-most part of the left and right sides experience some pretty hefty forces when turning on a dime - the larger the platform, the higher the forces - and you either need really good motors + rubber wheels (which need replacing often) or some kind of turning scheme to pull this off successfully on coarse ground, in my experience.