To me that was by far the easiest stage. Usually there's no reason to use a bunch of tier IV's. It's not so much for min-maxing as it is blindly making your weapon have the highest damage stats as though you don't have accuracy (or sometimes skill/spell speed) to consider as well. People usually say that you can cover your accuracy on other pieces but mysteriously fail to realize that you can cover DET/ crit on other pieces as well. It just depends on what stats you're getting from all of your other gear. You'd never be able to get it perfect anyway since the secondaries from everything else change every 6 months or so as it is.

Also even if you used no damage modifying secondary stats the weapon would be about 2% weaker than one using all crit/det. The difference is very minimal so just don't go broke on it.