Curved dragon greatsword will be stronger but you need to up your STR to 30 for the curved dragon greatsword but with it's B/S scaling at max it's a good investment far outdamaging a murakumo.
It is one of the strongest in the game for DEX weapons. High base damage with B STR scaling to boost damage definitely worth it.
Pate's spear or a roaring halberd DEX limits you to less options unless you don't mind C/C then a grand lance or a claymore will suit.
There's only two choices if you want miracles and staff hexes on the same thing sanctum shield or the black witch staff, out of those the staff is better.
The only three other problems I can think of are A) You have a soft ban for doing something wrong. B) You left in the middle of invasions too many times and are now cut off from Co-op(try using the bone of order to see if that's the case, if it is, it will be used. If not, it won't be used.) And C) The more likely case is no one is around your SM. 1.9M in NG+ seems really low to me, increasing that may help.
Dark infused STR weapon will give you much better returns.
Either a dark homunculus mace which is decently fast and has low requirements of 14/9 and deals strike damage. Or a dark archdrake mace a fast strike STR weapon a greathammer with a halberd moveset only weighs 6 units and has the requirements of 20/16.
Well that's build specific, if you don't have or want the stats for that specific shield, then it's a different story.
I use it only for the texture mods I turned everything off it still does hang when I like switch weapons or something and sometimes when a ghost player loads in for the most part it works wonderfully though.... I have like 5 or so weapons skin mods and just a few armor mods nothing really amazing lol I also have the blood mod but don't really notice it guess I should turn it on the 400% one.