About sign damage bonus, i don't really know, but with mutagens like madness one or concentration, you can give them a further boost. Also, certain swords/armors can boost this stat, even runes like the moon rune. Sign intensity is useful, also.
Well, those random loot diagram patterns or items in certain locations (mostly the burnt down asylum with the Nilfgaardian ghost), have really been removed from the game. You cannot get them anymore. They exist in enhanced edition for the console version of the game, like XBox. Repeat, NOT for old pc. Hell, you don't really even need them! The most interesting out of those was the Wild Hunt armor set; if you want a close equivalent, play dark mode and craft the final set, kinslayer. Beanshie, the sword, but the dark set ones are very good anyway. Even the normal ones, that are endgame, much like Caerme-Zerrikaternment (crafted), Dancer-Deithwen (loot, dancer from Roche path werewolf area) and Forgotten Vran Sword- Addan Deith (best normal ones), are very close to these removed items.
You don't really need them. Besides, main reason they were removed, was that they broke the game, up at the point you could pick them up. Play safe, and normally. Remember; Kayran armor, Jagged Blade, Superb Witcher's Silver sword, act 1. Act 2 is full of great swords and armors, you update them constantly, provided that you keep exploring each and every nook and cranny, including underground areas. And act 3 is where the endgame items are. Begin with Draug armor, then end up with armor of Ysgith for mage build (full of magic wraps), Vran for alchemist-swordsman (full of vran enhancements), coupled with Elder Blood set.
Post edited October 02, 2014 by KiNgBrAdLeY7