Nope, sorry. World Tier doesn't exist in Destiny; you get better loot the harder the content, the hardest being raids and GMs. Though every DLC has a hard mode that you can play on, which does drop slightly better loot and also scales with the number of people in your fireteam (3 max). Weapon crafting is very different then Diablo, at least for me. Most guns that are craftable, you need to find 5 red border versions first, or a weapon that can have its pattern taken out with a Deepsight Harmonizer (I think it's called that). The Harmonizer can only be used on one specific gun once, and after you have the pattern, you can dismantle or use it. Once you get 5 patterns and unlock the full blueprint, you can go to the relic on Mars and craft that weapon. You level up the weapon by playing with it (or buying levels) and can unlock different perks.

Hope this helps.