There's no question that if the SmartThings platform were stable, laying out a good network backbone for both zigbee and zwave should solve almost all problems.
Indeed, the fact that both zigbee home automation and zwave were existing third party standards that should provide a stable environment is the reason why many people with technical backgrounds chose Smart
Things in the first place.
Unfortunately, having a good network layout cannot protect you from platform issues. Obviously since people have been reporting issues with both virtual Devices and activities like disarming Smart Home Monitor, both cloud activities that are independent of protocol, adding repeaters can't help everything.
For example, just in the last month, community members reported the following:
1) Smart Home Monitor failing to disarm
2) mode not changing
3) timer scheduling events that are marked as milliseconds instead in seconds (meaning the event took 1,000 times longer to fire)
4) database corruption leading to rules and routines missing values
5) timed events being issued 12 or 15 times in a row (smart lighting, no custom code)
6) timed events being repeated again 15 minutes later
7) zwave controller becoming completely inoperable (not the end devices, the controller itself)
8) attempts to look at device detail pages resulting in either"Access Denied" or "not found" messages
Some of these have since been fixed. None of these would've been fixed by moving devices around in your home or doing a network heal.
SmartThings staff have verified these issues and there is much discussion of them, particularly in the following thread:
If your system is working well for you, that's great. I'm truly glad to hear it. And it's always helpful to understand enough about how your network works to lay it out efficiently.
But unfortunately, most of the problems that people have been experiencing for the last few months with Smartthings have not been due to a weak mesh. And can't be addressed by individual customers. They require platform changes, which the company has committed to making.
When the SmartThings CEO feels the issues are significant enough that he has to apologize publicly to the community, it's unlikely that local network configuration is the issue.
Absolutely, do whatever you can to make your own network as efficient as possible. That can only help. But in most cases the deeper solutions are, for the moment, out of our hands.