A bug for one client? not sure what are you talking about, I'm doing a comparizon because I work on software that run on a web server farm and everything I code it impacts on every client of the app. But hey, we arent talking about me so lets look on what the UO devs do or can do.
About the stress test "issue".. well, seems that you have knowledge on software development so you should understand that if you are developing a software that interface or is dependent to multiple components/software then you *need* to do
Integration Testing. If the software you are working on has 10k customers then its not serious to test the feature on a shard that has 1% of your customers but instead, you need to do
Stress Testing.
Its crazy that some people believes that devs do more tests because they now publish to two shards instead of one. Or three shard, if you seriously think TC1 does count as a shard. Thats not considered testing or QA (quality assurance). Publishing new features on these shards should be only used to get feedback from customers or maybe to get measures about usability but never for "customer testing" because you cant expect customers to do any kind of realiable stress, integration, security, etc etc testing.
I dont think mythic (now broadsword, same devs just a different company name) has any QA employee at all, so the responsability for testing each publish goes to the developers and the project manager (or producer, in this company).
Anyway, before a mod decides to lock this thread because people is discussing about something that isnt "on topic" then i willl add that... I'm too waiting on the Vendor search thingy and I'm too expecting some kind of communication from the dev team