It is my understanding that the landing gear is specified to absorb enough landing stresses, when operating within aircraft limits (mass and vertical acceleration), that the airframe is not subjected to more load than it has the ability (or design recommendation) to absorb. I also beleive, although do not have aerospace engineering experience outside Uni, that the maximum takeoff weight is more determined by the aerodynamics in terms of design lift available, and that as the aerodynamic design of the aircraft is refined an iterative process accomodates the landing gear weight (which correlates proportionally to some loose extent with the loads it is required to absorb) as supported by that aerodynamic lift.
The maximum takeoff weight therefore, is bound to be only a proportion of the loads which the landing gear can support. Landing at MLW at Maximum allowed ROD, plus the safety factor to which you refer, is much greater in terms of effective tonnage - as you showed with your calculations. Therefore I would write up a heavy landing if it exceeded the Mass-ROD limits specified in Std Operating Proc.'s for a normal landing. Otherwise it would be reasonable to trust that the standard loads from normal (SOP adherent) operation would be happily accomodated by the landing gear, and not fall into the 'heavy' category.
Hope that makes sense to somebody.
Edit: Rainboe, comparing relatively light landings with ones involving greater fuel loads in the centre of the aircraft: I would imagine there might be an effect from inertia at high ROD, effectively introducing an additional downward bending moment to the centre of the fuselage (NLG and MLG before and aft of this point acting as 'simple' supports in the model). Whether this would introduce greater tensile (under fuselage) or compressive (top of fuselage) stresses and if so, what the magnitude of them would be, I wouldn't want to guess...