The reason they look diagonal is contrast.
You shaded the highlights to look diagonal, and that is what sticks out the most from afar. It isnt until you actually zoom in that you notice the divisions between each brick and you know they're SUPPOSED to be bricks.
it seems you suffer from a grave case of detailitis, not everything is fixed by detailing. when dealing with a bunch of bricks it probably isnt a good idea to chuck as much detail into them as you can, try to make one simple brick and figure out some variations for it instead. Then you can use the simple brick for most of the wall, and *sprinkle* the variations on various parts of the wall to make it all seem more detailed.