300 sp A skill scoring.

I think you're misunderstanding how scoring works, right now the score o a character in arena is affected by:
- BST, which is the total number of stat a character has ignoring weapon, skills, merges and summoner support, your score increases every 5 points of BST (170BST scores the same as 174BST)
- Merges, your score increases for every merge your character has
- SP, is the total cost on sp spent on the kit of the character for the weapon assist special passive and seal, your score increases every 100 sp spent (2000sp scores the same as 2090sp)

If you do your calcs every character that has a refined non prf weapon doesn't get an increase of scoring with a 300SP A slot, while character that have a non refined non prf or a prf need a 300SP A slot to max their score