What you are saying makes sense. I have observed both 2DOF seat and full cockpit designs. In fact my motion base is designed to accomodate both and SimXperience will offer an F1 cockpit in 2010. IMHO, the reason that your statement holds true is as follows:
-Pitch, Roll and Yaw are output by the games less granularly (look at the min and max numbers in any profile to see this) therefore they are by nature prone to be more jumpy than the more finely grained g-force effects. Additionally, body roll is a contradictory simulator movement to lateral G-Forces which causes these effects to conflict.
-Jumpiness and/or jerkiness of effects can be countered in several ways
a.) proper dampening mechanisms
b.) adding load to the actuators
c.) reducing accel values
In the case of a full cockpit atop a motion base, the actuators are forced to move the weight of the drivers legs, steering wheel, pedals, and additional rig to support these items. This adds load to the actuators and therfore smooths the jerky motions. You can easily witness the smoothing effect of load on your actuators by getting out of your sim and letting the rFactor AI driver run a few laps. Without the load, the motions will be VERY jerky.
In my case, I desire to keep the load at a minumum which increases maximum actuator speed and life. In order to accomplish this combination of high speed movement and rid myslef of any jerky motions, I utilize hand adjustable dampers. The side benefit is that it makes the motion more fluid as it would be in a real vehicle without compromising actuator speed when making quick direction changes.
The concept of whether or not pitch itself belongs in a seat only profile is an interesting debate. I think that it is possible to properly mix this effect without adding negative motion queues and I think that Mike and Nima are getting close but in the end this is all a matter of personal preference.
I'll test your profile today in both scenarios. BTW, due to the increased load of your sim design, it is likely that seat moving sims will need to use far less accel when evaluating.