Here's my not-fast solution:

require 'set'

class Set
def intersect?(other)
other.each { |o| return true if include?(o) }
false
end
end

def distinct_sets(array_of_arrays)
set_of_sets = array_of_arrays.map{|a|
a.to_set
}.to_set

set_of_sets.divide{|i, j|
i.intersect?(j)
}.map{|s|
s.flatten.to_a
}
end

Adding the intersect? method to Set was primarily motivated by
readability, but also provided a noticeable speed improvement over my
original alternative (intersection.size.>).