You might like to take a look here
http://www.wineloverspage.com/forum/...hp?f=3&t=39034

I think your reasoning is sound.

"Ancient" is a very broad term, and I feel pretty safe in saying the
wine will have been of various strengths. But, yes, people often seem
to think that the wine was strong. A contemporary wrote about a wine
being strong enough to catch fire, and the amount needed to get drunk
was also discussed. But we will never get alcohol statistics from what
remains of historical records.

--
www.winenous.co.uk