Patch 3.1.1a is intended to be a very minor bugfix patch released a few days after the release of patch 3.1.1 to fix the paladinExorcism spell toolip.
Minor Bug Fix Patch 3.1.1a | 2009-04-23 00:48 |Aratil
In the next few days we'll be releasing a minor bug fix patch to version 3.1.1. This sort of patch is very small in size, and we use them to fix specific issues that can't be hot-fixed. Most patches require a lengthy testing procedure before release, but because this change is focused solely on a client tooltip, its testing process can be accelerated to resolve the issue as soon as possible.
In 3.1.1, the paladin ability Exorcism cannot damage other players, but the player game client does not display this change properly. Patch 3.1.1a will fix the tooltip to display the appropriate text; it also displays an error message when a player tries to use it against other players.
While we have not done many minor bug fix patches to date, we do plan to use them as appropriate in the future to resolve smaller issues rapidly, rather than waiting for a full patch.