Yes, but Legion does not use any of the weapons they are buffing, besides frags, and instead use lever actions, which are receiving a nerf.
True enough, which is why I said 'whether they/npc's use the weapons being changed.'
If they are going to nerf the Legions main weapon, the Cowboy Repeater, they should at least buff Legionaries, give them natural DR, higher END, higher STR, and higher tier weapons such as Trail Carbines or 10mm SMGs, make it so more of them spawn with guns or Rippers or Machete Gladius's.
One minor issue with that is that if you make the Legion stronger in those ways, then you also have to make the NCR stronger, because of some of the encounters/scenarios where Legion/NCR may fight, or those scenarios will become unbalanced towards Legion. Which means you have to change other things, and so on down the line.
This was made clear in an early version of the Increased Spawns mod, where initially the extra hordes of Legion were wiping the floor with the extra hordes of NCR because of extra hit points and weapon upgrade issues. Or something. It was very unbalanced in terms of NPC vs. NPC.