I still think, IMHO, the global Ajax events are better for this purpose. By better, I mean I think the code is more semantic.

Instead of inserting the element into the DOM each time, I just toggle the display:xxx visibility of the throbber from "none" to "block" and back. Make it visible in the ajaxStart event, make it invisible in the ajaxStop event. That would have prevented you from having the throbber added over and over again.

I bind the ajaxStart and ajaxEnd events to the document so it listens for all Ajax events.