Spamming a boss is considered a game hack not permitted to be discussed on the forum. See forum rules.
The game is designed to hinder the ability of people to reload and refight a boss to try to reroll different loot. So, it's not surprising it's not working.
Per the Wiki, two enemies have a CHANCE to drop the Lionskill leggings. IF they don't drop them, than nope, looks like you're not getting them on that playthrough. In that way, they are comparable to a handful of other hard-to-get items, such as the golem's fist or ring of unlife.
The Lionskill Leggings are nice, but they aren't the best in the game. In fact, if you're able to take on the named dragons, you're likely ready to start the quests needed to reach the Sunkun Citadel that drops the Leggings of Shadows (across the board better than the Lionskil leggings).
