It sounds very basic and linear, but a great start.
About 20seconds in the sound fails to create an impact. Make them bows sound big! the flames sound huge, get more leathery sounds in there for where the hand grips the bow, or riders grip reins etc. Layer up the sound of the horses and riders and use perspective, for example when you see the white horse fly over you.
There is no sense of the amount of arrows coming towards the white rider and deflecting the arrows is indeed weak. I think it needs the sound of wood hitting wood and the spinning of the spear would help... I think the high pitch whoooses would disappear now too.
These spring to mind but probably better examples out there:
Anyway good luck, think it will sound amazing once you add a bit more to it :)