Dork disk rules:

1. If the disk is bent, get rid of it.
2. If the RD isn't bent, and it goes into the spokes, adjust the low limit screw.
3. If the RD goes into the spokes and it's adjusted so that the upper jockey wheel is lined up with the lowest cog, you have a bent hanger or RD. Replace or align as necessary.
4. If nothing has worked yet, your freewheel cogs are bent. Replace freewheel.
5. If the RD still winds up in the spokes you have a crappy bike - or you are a crappy mechanic.

In short, a good mechanic should get any half-decent bike to work as intended without a dork disk.

-Kurt