Shrouds should help against out-of-band radiation. I'm no expert but I assume that they do more harm in a single radio environment than without but they should help when you have multiple radios next to each other.
Not only out-of-band, but also in-band interference from local and remote transmitters (whether direct by transmitters operating on the same channel, or indirect via out-of-band harmonics transmitted by low-cost radios).