Somnicide

For the most part that is true, but there are still differences in ranks between each shardbearer. For example, Adolin would be a lower rank than Dalinar. The unnamed shardbearer that a certain character killed would be lower rank, considering he wasnt even fighting at the plains where all the important people are. And I'm sure there are plenty other examples. True, shardbearers are considered the upper echelon of Alethi society, but there would still be slight disparities.

Which cover are you referring to? The UK Cover doesnt really have Oathbringer on it for the simple fact that it doesnt fit it's description at all. The in-book description for Oathbringer is: "Six feet long from tip to hilt. Long and slightly curved. A handspan wide. Wavelike serrations near the hilt. Curved at the tip like a fisherman's hook." The UK sword isnt tall enough, wide enough, or have any of it's distinguishing features. Whelans cover DOES apparently have Dalinar on it (I learned this two seconds ago), but I had never thought it to be him due to it being very ambiguous, the cape being the wrong color, and the sword not having the hooked tip. I had always assumed that was just an unnamed lower ranked shardbearer on the plains. I never even thought to question it, either. I decided to take inspiration from the art for Szeth's blade, but altering it to be thicker, more brutal, and more wedge-like. I did try to use my google-fu to find anymore of a description for Oathbringer (book is at Uni, Coppermind was down), but I never made the connection to the cover. Oh well.