To indicate that Sally's leg is still broken, stay away from the past tense (your examples #1 and #4). If you use the past tense the leg could still be broken, but past tense doesn't indicate that fact. If I say "Sally broke her leg yesterday" maybe you can guess it probably is still broken but if I say "Sally broke her leg 6 months ago" there's a good chance it's healed by now and past tense gives you no indication of whether it is still broken.
Similarly, to indicate that Sally's leg is still broken, stay away from the participial phrase form (your example #3). Especially in this context, a sentence starting, "have you heard", there is no indication that the action being described is still happening. If I ask you "have you heard about the mariner shooting the albatross?" you should not conclude that the mariner is still shooting the albatross. It could have happened a really long time ago!
The present perfect form (your examples #2 and #5) indicates that something happened in the very recent past so for something that takes as long to heal as a broken leg it should reasonably indicate that the leg is still broken, but to be absolutely clear have you considered the present tense? For instance, "Sally's leg is broken" or "Sally has a broken leg?" Because in that case there would be no doubt that Sally's leg is still broken!
If you say "did you hear" (past tense) it means did you hear at some point in the past? If you say "have you heard" (present perfect) it means did you hear at some point in the recent past? Both mean the same thing in this case.
There is no need for the sentence verb to be the same tense as the verb used in the gerund phrase (that Sally..). I can say, for instance, "I know that you wrote this question." The sentence verb tense should be appropriate for the sentence action and the gerund verb tense should be appropriate for the gerund action.
Note I've included a couple of sources that present perfect implies recent events since one comment on another answer claimed this isn't true. My understanding is there are 3 basic uses for present perfect: experience up to present (often with the word "ever"), recent past, and a recent journey. A broken leg would normally not be experience up to the present when combined with "did you hear" or "have you heard" (who says "did you hear I have broken my leg" if they are referring to their medical history from childhood?) so the choices are recent past or a recent trip. A recent trip doesn't make sense. So that leaves recent past.
"We use the present perfect simple with action verbs to emphasise the
completion of an event in the recent past." Cambridge Dictionaries
Online
http://dictionary.cambridge.org/us/grammar/british-grammar/present-perfect-simple-or-present-perfect-continuous
"The present perfect is often used to express recent events that
affect the present moment." About.com
http://esl.about.com/od/grammarstructures/ig/Tenses-Chart/presperf2.htm
"we often use the present perfect for recent events" wordpress.com
http://englishprojectoxford.wordpress.com/2013/10/24/present-perfect/
I believe "have been finding" indicates that action started in the past and continues (or effects of this action continue) into the present. "Have found" indicates the action has been fully completed in the past.
This may be an ongoing activity if they are still "finding" or observing these adaptations, i.e. their research has yet to cease.
Best Answer
Ah, present perfect versus simple past... the joys one can find in the nuances of verb tenses!
Three questions to ask yourself when deciding whether to use the simple past or the present perfect:
Has the time period of the action finished?
If the time period has completed, the simple past is in order. Otherwise if the time period is still ongoing, then use the present perfect.
In your sentence here, you're acutally referring back into a previous time period when people were actively in a situation, so I believe have found communicates the state of the person in question better.
Is the point in time specific?
Specific times generally use the simple past, whereas unspecified times can get the present perfect.
We don't really care exactly when the person found themselves in the situation in your sentence above, but we know it happened at some time before the time period being referred to in the sentence.
Has the action finished?
Finally, already-completed actions can get the simple past, whereas ongoing actions which started at a time in the past receive the present perfect tense.
Again, in your case, her wails are for people who are presently still in the (presumably) travailing situation which the song is about, so the perfect tense is more apt than simple past.