QA Build 1257:
Town Vendor Search performance has been much improved. A tweet mentioned a 5x performance increase, but it seems a fair bit better than that in large towns. There is still a reasonable delay in the most populated vendor towns, sometimes over a minute, but others load in seconds.
Update provided by Coswald Dirthmire: https://www.shroudoftheavatar.com/forum/index.php?threads/today-on-qa-r93.169904/#post-1330288