It's generally accepted that using Avios for long-haul economy flights is a poor use for them.
If you pick a flight (as in a single flight) that is close to upper limit of a distance band* on a carrier that charges little or no YQ, economy redemptions can be a great value. BOS-DUB, @ 12.5k points and minimal fees, comes to mind. HEL-PEK @ 20k points is also nice.
*I don't have the distance bands in front of me right now, but if memory serves me correctly, once you start looking at flights >5k miles, BA points start to suck no matter how low the added fees are. At that threshold or above, AA points are a much better currency.