I'm new to this and my head is swimming with questions
 

Sit: Runner on third, Pitcher pitches to batter, batter hits hard line drive back up the middle hitting pitcher in the nose or eyes, pitcher collapses...can you stop play immediately? If it was a DB would it be delayed or immediate?

IMMEDIATE DEAD BALL.... Get medical attention...figure out the baserunners later.....

Your action is based on whether any delay might worsen the effect or risk for the injured player. Your example of a head injury is one for immediate stop, as opposed to the ball skimming of a leg, or a twisted ankle.

ASA was very smart in incorporating this kind of scenario into a concrete rule (Rule 4, Sec. 10). Kill the play, get immediate medical attention to the injured player(s), make the awards when you're ready to resume play. It's better to err on the side of caution than on stubbornness.

thats what i was thinking
 

I couldn't imagine the rule going against common sense. thanks for the help

Ohh ... there are plenty that go against common sense. ;) Fortunately this one does not.

This rule allowing the umpire to kill the ball on a serious injury was a fairly recent addition, wasn't it? It seems not that long ago that the official rules were to play on. Or, maybe my memory is not correct...

Documented as a rule versus general practice, which I believe was as I said above. Somewhat like the "step & reach" concept.

It's only been a couple of years for ASA. Good chance other organizations recognized this prior to ASA making the change.