User blog comment:Neppudere/Time to lay down the LAW: Legendary Archwitch Guide/@comment-13020706-20150925102211/@comment-13020706-20150925164016

Here's what I think:

1) There's no buff # cap. I've tried Super Iroha + Skill Unleash. In comparison to Huang Long, damage is still capped at ~3.2m.

2) There's no buff % cap. Used a card without any arcana boosts to ATK. Damage is still capped at ~3.2m.

3) There IS an ATK value cap. All evidence so far proves this, both factually and logically. There's no evidence to the contrary. You have to keep in mind. If there was a damage cap, the damage would actually be capped at some value and would consistently be that value. Instead, damage is within a range of values which supports the hypoethesis that ATK is capped.