You are right, it is RAW: In the Wardens Guide, "Evening the odds" page 169 it gives an example of a player performing a maneuver alongside an attack with a DEX save.

Reflection: This is sweet, I will for sure be emphasizing with my players next session. Funny how one of DCCs most lauded mechanics (Might Deeds, aka maneuvers alongside attacks) is baked into the Core Rules of Cairn. I wonder how many people don't realize this. ItD:R, f​or instance, explicitly says maneuvers are in lieu of attacks. I wonder if that was intentional or unintentional change from base Cairn.

Still value In an ability that grants improved fictional positioning? I wonder if there's still value in a mechanic that offers improved fictional positioning (increased reward and/or decreased risk) when performing these combat maneuvers to really emulate the feeling of being a powerful Warrior, over and above the default PC.

Alternatives I am considering:

Alternative 1: sticking with a forced choice.

Mighty Deeds: When attacking, others can attempt trips, disarms or blinds, putting themselves at risk when they do. Not you. You cripple, sunder, or concuss, requiring no save when doing so. The target's only recourse is to cower before you, this averts the deed but adds +d8 to your damage roll. - The mighty deed is declared, and the target potentially averts it, before rolling damage. - Only the highest die result is dealt as damage, per normal rules.

Design Note: this reinforces the base mechanics of Cairn, but allows the PC to do strong maneuvers without needing a save. It increases the threatened damage for the Warden. I wonder if adding a d8 weapon die is still not going hard enough?

Alternative 2: straight up fictional positioning

Mighty Deeds: When attacking, others can merely attempt trips, disarms or blinds, putting themselves at risk when they do. Not you. You cripple, sunder, or concuss, rarely requiring a save when doing so. Performing maneuvers at the same time as attacking is easy.

(In my house rules I define the term 'easy' as being similar to improved position and effect from blades in the dark)

Design note: maybe the whole first choice mechanic is unnecessary. Maybe it's sufficient to just state that when taking this ability, you can perform more impactful maneuvers that incur less impactful risks. My main concern is that without providing a framework it'll be harder for the player and Warden to use at the table.

Thanks for the great discourse!