No , for that kind of champs , ATK stat doesn't influence on a damage done . So you can ignore it , for now ... )

Alkenn said:

For defence based champs where all their skills scale off defence, does atk contribute in any way, or is this a totally wasted stat?  If it does not, will there be weapons in the future that have stats other than atk?

That will differ from one case to another, but, if a Champion has all Skills scale on another Stat, ATK will indeed be much less useful to them. It will still add to the damage as far as I remember, but much less so than usual. At the moment I am uncertain if there will be Weapons with DEF, but I will try to check next week and see what I can find!