it looks like the progression of gun guardian weapons is the following:
vorpal slashers (ilvl 37 6 slots) direct spectral 400rpm
vorpal rippers (ilvl 47 6 slots) direct spectral 400rpm
pistol swords (ilvl 58 4 slots) direct spectral and spectral splash 1m 400rpm

the loss of 4 mod slots worries me a bit since that’s just a huge decrease in damage.  has anyone found any 600rpm pistols at level 50 yet?

the other thing that’s kind of a huge change is there’s a level 49 nova gun called the joint gun that has 5 mod slots and does novas every 2 seconds.  55 acc to equip only 1 but 5 slots might make it better than any 1h sword

proc damage is based on mod ilvl so i’m not sure using mods in the 30-40 range against 55 mobs is really going to be that effective.  at the very least you’d want rippers just because of the fact that cata runs are endgame content and will generate more mods over a longer period of time than people grinding from 30-49.  your only option if you want to use that ilvl 63 10% shrapnel mod from hell moloch is either a pistol sword or a mm/engie with money to burn

mod ilvl is definitely the case for novas but since its gun guardian novas really arent a big endgame concern at all.  it might be the case that procs that come from enemies are based on ilvl and procs that come from you are based on character level or maybe it’s just all ilvl.  if it’s the former, then you can have shrapnel slashers and call it a day but if its the latter then that kind of sucks.