since the rifle special ability 'Dead Eye' says it does max damage if it hits, does that by default also trigger the Dire Strike effect for the d6 STR damage? Or does it not trigger as no damage die was rolled?

Good question! You’re right that since you didn’t roll any dice, you can’t trigger a Dire Strike. Thanks!

another question connected to the first. Does this mean that the Dire Strike effect listed there (and by consequence the Scattergun above it) trigger during regular shots with these guns that roll max? I had falsely assumed they were only checked when the special ability was used.

Ah, I see the issue here. At the moment, you either get a Dire Strike with every use of Dead Eye or it never triggers, depending on how you interpret it. I’ll fix this in a future update to have Dead Eye grant Damage Advantage instead of Max Damage; this gives double the chance to get a Dire Strike.

The Special Attack Dire Strikes do only trigger when using the Special Attacks, not in standard use.