At the beginning when no one really knew how to deal with Keep Away Arthur was amazing. But now he just has so many opens to the rushdown characters.
Personally having Morrigan as Anchor is where she should be. With her Dark Harmonizer assist, building you meter by 30% while gaining meter while doing a combo. For that Zero, Ryu, Morrigan team use Ryu on Point. With Zero in second and Morrigan as anchor. Morrigan is one of the best anchors in the game imo. With level 3 x-factor and her illusion hyper she has the potential for some of the best mix-ups and shenanigans. Plus comboing into her level 3 is really simple and with level 3 x-factor I've done almost 2 million damage combos.
In all honesty though, get rid of Ryu. When I run Zero I personally like using Wesker with his gunshot assist, since it OTGs and you can extend combos and setup unblockables with Zero on point. And if you do run Zero, Wesker, Morrigan. Either Morrigan or Wesker are amazing anchors.
Also what assists do you run with your characters?