Sorry if I bust your bubble here but the odds of non mythical items changing stats is extreamly low.

If you've noticed there are very few top players who use physical mechs, so if anything, the weight of physical weapons should be decreased due to the popularity and effectiveness of heat and energy builds.

I'd say there is a good chance that the weight stat is calculated through a "master equation" that all weapons stats are plugged into. Obviously minor changes need to be made at some point or other (update we had today for example).

The stats of all Epic and Legendary items have been perfectly fine through the past year that Iv played through, no need to change them now.