I ♥ associativity! comp is associative and optimized up to arity 3, let's leverage it! (I ♥ commutativity more, though)

balance.clj

(defn- balance [n f & args] 
  (if (> (count args) n)
    (apply balance n f (map #(apply f %) (partition-all n args)))
    (apply f args)))

;; optimization kicks in for N >= 4
=> (doseq [N (range 1 16)] 
     (let [++ (apply comp (repeat N inc))
           b++ (apply balance 3 comp (repeat N inc))]
       (println "N=" N)
       (time (dotimes [n (/ 1e7 N)] (++ n)))
       (time (dotimes [n (/ 1e7 N)] (b++ n)))))
N= 1
"Elapsed time: 314.49 msecs"
"Elapsed time: 283.901 msecs"
N= 2
"Elapsed time: 523.819 msecs"
"Elapsed time: 510.677 msecs"
N= 3
"Elapsed time: 389.977 msecs"
"Elapsed time: 408.597 msecs"
N= 4
"Elapsed time: 1537.677 msecs"
"Elapsed time: 492.707 msecs"
N= 5
"Elapsed time: 1225.063 msecs"
"Elapsed time: 503.592 msecs"
N= 6
"Elapsed time: 1245.603 msecs"
"Elapsed time: 492.784 msecs"
N= 7
"Elapsed time: 1087.398 msecs"
"Elapsed time: 370.495 msecs"
N= 8
"Elapsed time: 1295.758 msecs"
"Elapsed time: 434.075 msecs"
N= 9
"Elapsed time: 1084.12 msecs"
"Elapsed time: 334.002 msecs"
N= 10
"Elapsed time: 979.564 msecs"
"Elapsed time: 424.21 msecs"
N= 11
"Elapsed time: 965.945 msecs"
"Elapsed time: 346.99 msecs"
N= 12
"Elapsed time: 1100.682 msecs"
"Elapsed time: 347.335 msecs"
N= 13
"Elapsed time: 933.35 msecs"
"Elapsed time: 353.287 msecs"
N= 14
"Elapsed time: 897.669 msecs"
"Elapsed time: 366.5 msecs"
N= 15
"Elapsed time: 866.187 msecs"
"Elapsed time: 373.318 msecs"
nil