I realise that this could be open to abuse and that some might report threads on that basis anyway, but sometimes threads come up that are so sick and depraved that they need urgent attention as in within minutes. If there was an option to report as needs urgently looking at next to the spam and general report check boxes then these threads could be reported as such and then addressed as priority.
The alternative is that there are threads which get multiple reports but it stil takes HQ a while to respond and meanwhile the threads build up a number of postings and the OP gets more and more attention. And this is when people are far more likely to troll-hunt.