Maybe YTTalk can create a thread that YTTalk members can reply if they allow video responses and genre/category of the channel and whether it is manual/auto approve?
With big channels, I agree that you might not get as much exposure since it gets bumped down rather quickly. For smaller channels that are growing somewhat bigger than yours but with less video response, then your video might stay there for a few days (this is the kind of channel that I am on a lookout for). If your channel is new, then even the small exposure might help. Like you don't have to do it all the time, but just do it every now and then so that you have varies traffic source instead of just one traffic source method.
I tried a big channel one, where there is already 7 pages, that is not good haha. No point video response those as I doubt anyone would be weird like me to go through 7 pages to find interesting videos >_>
I also tried a smaller channel that is growing steadily, I posted a video response (relevant response). It is not driving a tons of traffic, but so far that video is the most popular video in my channel (the channel is new).
I only have these 2 examples since I don't have many videos nor experience yet. But maybe someone else has similar feedback like my 2 examples? :]