Ive played U/W Heroic against my deck and beat it 2-0, ive also played it in cockatrice, while it was nice, I definitely didnt like it over what im running. If you dont think warriors arent valuable enough to protect then perhaps you shouldnt be playing this deck, seeing how they rely on each other. Arashin isnt the only one that is valuable enough to protect, both the chiefs are just as valuable.
Scale is great against control. It takes your weak 2/2 creatures out of blight/sorrow range with simply 2 scale or 1 scale and 1 spear of heliod, forcing them to use more cards to get rid of whatever, then you can simply protect it, or it simply guarantees more damage done before they use a board wipe.
 
On Arashin; she is simply too slow for me to want 4 of. Yes she is great, that much is known, but 3cmc and only 2 toughness. Since you dont want to run scales MB and dont have any protection cards except 2, shes just too weak. Rager's ability is nice but you seriously only need 1 of him on the field or youre paying 2 mana for a 2/2 if you already have one swinging. I suppose it makes sense in this deck since youre going raw, but against control, having more than 1 on the field will be utterly useless since they typically only have 3 creatures maximum and against aggro, they typically arent going to be blocking much anyway so he simply becomes a 2/2. Unlike yourself I have playtested it. Even though it was cockatrice and thats how I felt about it.
 
I dont remember if I stated before, but I have ran this card. I used to have 2 in my deck, and yeah it won me games where I used it, but 3 is too many, the most amount of warriors I was ever able to get back from my graveyard was 4 and it completely sucks against anything that exiles your stuff.
I also find it funny you dismiss shadowspear, yet call Woe-Reaper the best white warrior 1 drop. And I already did name a better 1 drop in standard that isnt easily removed by sweeps and shadowspear is it, though yeah it becomes a 2 drop because of dash, but you do have the option to cast it regularly and shadowspear will always get you 1 damage through even if it's blocked and forces opponents to use instant speed spells.