Right. What they should do is have a special hard mode raid final boss drop (let's call it a mote of solar/arc/void) that bestows elemental damage to any legendary weapon. THAT would add weapon diversity while still requiring end game activities to acquire. Raid weapons could still be differentiated through special useful perks.

Some sort of system for elemental transfer would be interesting. My fear is that we will all be using the same elemental primaries again in a few months...