When we were doing the profiling while developing the optimizations, we were surprised to find that the Javascript thread was spending something like 50% of its time in the method to remove a DOM element. Now, maybe that's because Angular is not removing DOM elements as efficiently as it could, but it was a bottleneck.

You are right though that optimization #3 is a big hammer that helps reduce the need for the other optimizations, but in the end, we found using both gives us the best result. And the other optimizations which much in terms of code.

We are using version 1.1.15 and already had AngularJS re-using the pre-existing DOM elements if it could. When we tested it (without optimization #3 turned on), we found that it still had too much lag so felt it was better to use the DOM caching optimization.