You realize Moria used Doppleman to lead Luffy all the way across the castle and was on a totally different side of the island, right? Gear 2 isn't enough to make up for that kind of trickery or distance. Doppleman IS a legit tactic for Moria to use, its part of his power base.
Moria outsmarted Luffy consistently and had a whole bag of tricks to mess with him.
Moria's ego is what got him in the end, more than any other factor. He assumed Oars would come under his control sooner rather than later. He had the shadows of all the strongest Strawhats, he could have just waited a few minutes till day break and then their power would have been greatly dimished. Or he could have just absorbed 10 or 20 shadows to enhance his own strength, instead of trying to show off with 1000.
Or he could have accepted Kuma's help when it was offered.
He was a completely credible competent threat capable of destroying Luffy, but it was totally his ego that did him in, on multiple accounts.