you think its worth getting/using

Its worth getting lucky imo

of course

simple

you're not even on the same textbook let alone page as the question asked.

It is worth getting if you have a very large gap in avg damage (looking at you lightning) otherwise it's sort of minimal gain for investment
Luck is a mechanic that rolls a number twice, with Lucky rolls applying the best result, and Unlucky rolls applying the worst result. Modifiers that state "when Damaging" refer specifically to damage ranges, and not related mechanics such as accuracy or critical strike chance.

For people who can't read ? It's optimal at 50% btw.