This is true -- the Warchanter is attempting to prevent everyone who might assist in the check from using attack spells or weapons, and it's done by having all characters make a wisdom check.
At the very least, the Warchanter's description should change from "you" to "all characters" to better communicate what is happening.
Potential assists that are blocked by a failed wisdom check include Ranged weapons. I thought that spells like Corrosive and Lightning Splash would also be prohibited, but these do not have the Attack trait.
