You would add a considerable amount of time in the process of loading this data by doing each table request seperately. It actually shouldn't take any more time (that would be reasonably noticeable by a human) in receiving one data table via AJAX vs receiving all 30 via AJAX. Essentially the time it actually takes to send that data back and forth doesn't really increase per request and it would merely be a matter of processing time on the server-side script end of things that would increase.
"Given billions of tries, could a spilled bottle of ink ever fall into the words of Shakespeare?"
I would recommend making one Ajax request for each table, but staggering them by, say, 300 ms, and doing them in batches of 5.
This gives you several advantages:
1) The real processor heavy work for the browser is rerendering the page. You have more render events in the browser, but less of the document is changed each time.
2) With staggering these updates, the processing time is spread out over a greater span of time, causing fewer cases where the web page freezes. You get greater average processor usage over the life of the page, but lower spikes in usage.
3) By staggering requests and doing them in batches, you can guard your backend against what is essentially a distributed denial of service attack by your own users.