would an o-ring, or moon gel sort it, or am i just tuning it wrong?
Yes, possibly, to both questions.
Muffling would help tame overtones, regardless of the cause.
Tuning, particularly making sure the heads are balanced in tension & pitch from lug to lug, can help tame the bark of nasty, dissonant, ringing overtones. The pitch relationship between top and bottom heads also plays a part in a drum's sustain. If they're tuned to a consonant interval (same pitch, thirds apart, etc.), the heads will vibrate sympathetically and tone will sustain longer. If they're tuned to non-consonant intervals, the vibration of the heads won't sync. They'll actually work against each other using the column of air inside the drum to affect each other's vibration, and sustain will shorten.
...and some drums are more prone to ringing than others. Choice of heads can have a big effect, too.