Traffic Shaping Limitations
ALTQ shaping is not capable of setting an upper limit on traffic. Use Limiters for controller upper limits.
but HFSC explicitly has an "upper-limit". I dunno about other ALTQ algos but the quoted statement doesn't seem accurate. (ALTQ itself has an upper-limit on a per-interface basis with it's Token Bucket Regulator, but that's likely not what the quote is referring to.)
Some clarification regarding why limiters are being advocated over ALTQ for per-queue upper-limits would be useful.