MichaelSomething
Legend
@Ashkelon I agree with @Jester Canuck that there is the kernel of a good idea here.
You and others have identified the two main drawbacks, and I don't know if there's a way around them:
1. Multiple attack vectors are more dangerous than single attack vectors. 10 goblins might actually be more dangerous to an individual PC than a dragon. There is fiction-rules dissonance there, unless there are further rules to limit this, or dragons are designed as multi-attack whirlwinds.
That could be considered a feature, not a flaw. After all, it would be more realistic for a large group of beings to overpower an adventurer by sheer force of numbers....