I have worked in the IT field for many years and worked on major releases as well. Even with all the downtime. This has been a very good launch. Taking the servers down to perform maintenance and fix last minute issues is perfectly normal.
So it was down for 12-14 hours. This was planned and approved by thier managment team in order to fix potential issues before launch. Performing the maintenance they are doing right now 3-4 hours is also very awesome.
From an IT perspective you are seeing a team doing what is called as preventative action and corrective action policies. You want to have a team devoted to addressing issues. If they didn't take down the servers and fix issues before launch or perform this quick 3-4 hour maintenance i'd have been very worried.
It's when you have games that give a 5 day head start and then don't do anything during those five days to fix issues, and have massive downtime on launch day that scare me.
ESO's technical people on their end are saying "hey we noticed some issues in these areas and we recommend fixing them before launch". Thier managment team listens. That is a good team.