Important: despite use of the term, a harmonic damper is not a balancer.

The SEMA damper standard (S.F.I. 18.1) does not rate a damper’s effectiveness, or certify that it works at all (let alone on a specific engine) - only that it fit the designated engine, and didn’t explode during the test. Their interest is limited to safety and qualify control, not specific engineering results. I couldn't even find a requirement as to how accurately it must fit the subject crank nose.
Any bonded rubber damper lives or dies on the manufacturer's reputation. MoPar fairly good on a stock engine for quite a while. An unknown damper (China and ?) may not only disintegrate (rim flies off) but fail to properly damp the harmonics (not the reciprocating mass) of the target engine. The rubber dimensions and characteristics are the whole works: the rubber insert has specific properties, including hysteresis, durometer hardness, &c. These factors are partially chemical in nature, and not easy to analyze or modify. What the rubber is made of (how much sulfur, &c.), what vulcanizing temperature, and how much it’s compressed to fit the space all play a part. I've never heard of any test for effectiveness, only for "how bad is the condition?".
The damper’s rubber ring will naturally decay with age, mileage, exposure to hot chemicals, vibration, ozone, and ultra-violet light, and become unsuitable for even a stock engine, let alone high performance or racing use.
Visible signs of damage and potential failure include:
» the rubber is partially missing
» the rubber is discolored gray or “chalky”
» the rubber has surface cracking
» the rubber has been partially extruded
» the damper rim is dented or bent
» the damper is loose on its hub or on the crankshaft nose
» the damper rim has excessive run-out (“wobble”)
» a “squeaking” noise that defies detection
If you have any doubts about the integrity of a factory damper, remove it (and rebuild it, if you wish).
Even a high-mileage (but apparently undamaged) damper has lost some effectiveness due to hardening of the rubber parts, which also changes its frequency range. Even if not damaged, it’s not doing the job if it doesn’t “float” the inertia ring as it was designed to do, which is at specific RPM points (not continuously).
The bad ones I’ve seen that we know slipped (the engine won’t run with the ignition timing marks aligned, but seems OK if you tune it “by ear” and check for pinging) all look damaged, but this obviously only catches them when they’re toast.
If you can rotate the outer rim on its hub more than a few degrees with a strap wrench, &c., it’s gone.