In the current meta, catachans - even with straken, harker and a priest nearby - hit like a wet noodle.
Vs. dedicated close combat troops, your infantry squads will be long gone before you can even consider using Fix Bayonets.
Its definitely not optimal because guards have tshirt saves and a 3t but it would be funny if a unit if assault intercessors charged a blob of infantry and the next turn were killed off by the same unit. In melee.
Those Intercessors would get 41 attacks, 27,33 hits, 18,22 wounds, 15,18 dead guardsmen.
2 guardsmen sergeants and ~3 regular guardsmen retaliate. There's no way the intercessors are "killed off".