Righteousness (cleric class deck) is a spell that adds d6 to a combat check - should it have the "attack" trait?
Based on the card text as written, no. "Attack" trait tends to be attached to spells where the text is "For your combat check...", whereas Righteousness is a buff spell, along the lines of Strength, Speed, etc., that adds to all of your combat checks during the turn. Unlike the turn-length mage spells, it only affects your own checks, and not anyone else's, so it is more like a buff than an area-attack spell.
Short answer: I don't think so.
Shame.
Having the power to return recharged "attack" spells to the top of the deck with Zarlova is a lot less use once you realise there are no such spells from levels 1-4 (I don't count "Fear" as it's just an evading spell, and thus a waste of a card...
Based on the card text as written, no. "Attack" trait tends to be attached to spells where the text is "For your combat check...", whereas Righteousness is a buff spell, along the lines of Strength, Speed, etc., that adds to all of your combat checks during the turn. Unlike the turn-length mage spells, it only affects your own checks, and not anyone else's, so it is more like a buff than an area-attack spell.
Short answer: I don't think so.
Although, now I look - things like Incendiary Cloud have the "attack" trait despite only buffing existing checks, rather than defining them
According to Chad, the Attack trait tends to mean more that the spell targets the opponent instead of the character. There is a little more to it, as there are some exceptions to that over simplification.
Attack Trait spells have a direct or indirect effect on an opponent.
The Clouds damage opponents in the RPG, and that's where it translates over, whereas Righteousness boosts your allies even though it increases the 'damage' you do against an opponent.
Pretty much, it's the difference between affecting the opponent and affecting yourself or an ally.
In the card game, both ways end up adding to the check or adding dice (usually) but the way it does so is slightly different.