Honestly, their stats are not that bad, especially centurion DT.
However, their whole idea is focused on conquering and gaining stuff from their opponents. So, it makes sense their mish mash of armours. They still have got infrastructure but it is kind of crap. I mean Legion forbids stimpaks, chems, autodocs, energy weapons etc. I remember Legion ambush for merchants by 4 recruits, 9/10 Merchants win without losing anyone or 1 person at most. They really needed more time to develop them.
The reason NCR has not won over them is because:
a)Oliver is a complete idiot, who sat on his ass for years doing nothing.
b)They are overstretched, corrupt.
c)Mojave is draining them dry.
Still, there is that Legion Redesigned Mod, which gives Legion a lot more oomph, but it is too much canon breaking to me.
