Originally Posted by
MN_14
Waste not II is definitely a useful skill, but it's also a double edged sword. There are many cases in which I forgo the use of WN2 in order to come up with a better rotation on the fly. Over-reliance on it can sometimes be detrimental.
CS2 is useful in that it's more powerful than basic synthesis, possibly allowing me to use tricks of the trade one extra time when using maker's mark/FS (depending on my craftsmanship stat of course). Since it's RNG free, it also can save me 22 CP in some cases.
I don't consider either to be essential but recommend having them both available if possible. When crafting base 2* materials, I usually have both equipped.