Everything that has moving parts "might fail" and a doser is definitely capable of ruining a tank.
You can spend more in hopes of reducing the likelihood of early failure. But that doesn't do much for other bugs (i.e. software) or eliminate the possibility.
Really, those are trade-offs for automation. I dosed my tank manually – by hand – for the first several years. That eliminates the cost and early-failure concerns, but you've only traded for a different set of possible problems. You still haven't eliminated the risk.
That's not to say you should either dose by hand or spend up for the GHL....it's just to say there are always risks, even with automation.
There was a recent thread of a doser issue that was solely due to a software bug. The bug just so happened to also defeat layers of additional security that were added to prevent just such a thing from happening.
Spending extra money or effort or using the most popular equipment (etc) will never help in those cases....you just have to be prepared for them.
For example, that can mean to always be prepared to do a big water change. It's a little bit of a pain, but I can almost always do a 50% water change. It also means do not leave the tank unattended for long periods....it should get no less-frequent attention than a dog or cat would. If you're frequently away for long periods, a professional tank-sitter (or different hobby) is in order.
