Can Raven Horn Baselards come above average anymore?

Does that apply to equips that aren't in KMS? Almost every SW weapon I've seen is 2-5 above average.

It applies to everything. The reason Sweetwaters have stat variation is because the mechanism by which you get them (through the NPC), forces stat variation (in this case, purely positive). I believe Gach does as well (but both positive and negative).