Regarding patch updates uploads for addons by others.
 

What is the general rule of thumb in regards to this?

I have made some client-side patches to fix some addons for myself, the authors appear to MIA as I have messaged them and they have not replied, nor have they updated their addons in a month or more for various fixes which I have covered in my own client-side patches...

Just wondering what other developers think as I have full respect for authors and am not wanting to step on toes.

There is an explicit option when you create the addon for whether to allow optional files/patches etc for the addon. If you go to the Optional Files page and see the links for upload, they've allowed it, so go ahead.

As well, some authors will state a license for their addons. If it's an open source license (GPL, BSD, MIT, etc), you are allowed to release it as an identical addon just changing the name as long as you attribute the original author (depends on license exactly what's needed for that). Patches would definitely be ok, as well as just maintaining it yourself as a new addon. For one of the major licenses, Google or Wikipedia can help a lot on what exactly you can do.

If there isn't a license and they didn't opt-in for patches, it's fully copyrighted except as covered in the Zenimax TOS and you can't do anything without their approval.

Cheers Sasky, just that I've recently started to get my cogs whirring around the .lua coding, there are some addons that I use that are in need of some patching with small fixes, some typos, some localization of variables, etc. Guess I've got some more reading to do before I decide to push public patches, etc.

I assume you have posted these fixes, typos, localization problems you have found on the addons' pages ? That should always be your first port of call just in case the programmer is still active and hasn't noticed those problems yet.