That's true. There's nothing good to pair it with if you only want to invest in one proficiency skill. I was thinking about a build with heavy armor, so I can use Shadostalker and the worn plated gloves. Then Chaosreaper, and the BSS to balance the AC penalty out a bit, which would require two proficiency skills for the weapons. The heavy armor would give plenty of BC, so I would plow levels ups into AD and AC, again to counter the AC penalty of Chaosreaper. 2 x Villain's ring, again for the AC, but also for the AD. Give up on criticals completely. That would give me three pieces of gear with actor effects, 4 attacks per round, and reasonable AC and BC.
Level: 64, XP: 4734786, HP: 196, AC: 246%, AD: 49-59, AP: 3, ECC: 25%, CM: 3, BC: 127%, DR: 2
Gold: 232355 | RoLS: 1, RoL: 1, GoW: 1
HH: 1, CS: 2, IF: 4, Ev: 3, Re: 2, WP:DA: 1, WP:1S: 1, AP:L: 1, FS:DW: 2, S:DW: 1