Adding more moderators will only solve the problem you addressed is if you specifically look for moderators who can monitor the site during specific time frames when posts seem to go over an hour without at least an acknowledgement response. For example, if posts made between 1 and 3 pm seem to be unacknowledged for over an hour, then the solution would be to have a couple of folks "assigned" these time ranges. It would take several because any of us could be tied up and not able to actually be watching the site during our routine time.
I think we all try to watch for new posts, and I know you aren't suggesting that we are slacking. Do they always appear on the home page? If not, can they - at least on our home page? Or, and probably easier, could a page be created for moderators that lists the first time a topic is posted and the number of responses so we'd know if one was missed. I've tried watching the forum listing for this, but seem to still have missed one here and there, especially if several things hit the same forum fairly close together.