Hi and welocme. Daggers in D3 have the highest attack speed among other weapons but they are rarely used. There are some builds that use them of course (Crusader Aegis, Shadow impaler Demon hunter, to name a few) but from what i know they are not used by a typical Barb build. In your example, your Oathkeeper has 1.30 attacks per second while your Eun-Jang-Do has 1.50. Appart from that, it doesn’t offer anything else in your case. There are certainly better weapons in slot than that, but that doesn’t mean that you cannot try it. Usually, this dagger (Eun-Jang-Do), is equiped by the Templar (i.e. the one of your followers) in conjunction with a shield called “Freeze of Deflection”, to offer some additional cc and stuns.
In your case, i can give you some suggestions for some other weapons to pair with Oathkeeper. Echoing Fury (if you are leaning towards a speed build), Azurewrath (probablty the best in slot, thanks to cold damage + chance to freeze) and lastly, my personal favourite, The Burning Axe of Sankis (for more toughness, cause there is a chance to cast Ignore pain on yourself whenever you get hit by something and Ignore Pain is a big defensive buff for barbs).
There is a general rule that if you find a primal, if it is not the best in slot with everything rolled correctly, do not try to fit it in your build. As much as it sucks, some primals (if not most of them) are usually worthless.