Major errors are easy to spot and will likely take QA minutes to find. They're also probably not going to do a full test of the entire system with every change

Major errors are easy to spot and will likely take QA minutes to find. They're also probably not going to do a full test of the entire system with every change unless you've got a very small product. One thing I've seen that I like a lot is individual changes creating individual front ends. You test the one thing in that change, and it's done. This tends to cause a lot of problems with CORS, but then what doesn't? Agreed with you though that good code reviews (whatever that means) obviates most of this.