In lv 30-40 range, the stuff for demo/necro drop in Black Castle (minor pieces, lv 32 but very good), in Pyramid of Ancients epic (dagger and tali), then vanaheim armour lv 39 (vanaheim rank 2 vigdis), Chang (eleven sacred weapon) at lv 40 (Purple lotus swamp).
In lv 40-50, open-world blue drop (in epic Field of Dead for example), hands dropping in Toirdealbach dungeon (not the neck, you can have better in armory reaching pvp 1), hands dropping in Cradle of Decay, weapons in the same dungeon.
At lv 50 you can do ardashir arena and get the epic staff lv 55 for the next bracket.
Since lv 40 you can even craft gear for your demo, but the armorsmith progression is demanding as time (expecially for rought leather dropping) and costs (You prolly need to buy gems even if u cut).
Some dungeons like Sanctum, even if beautiful, have little o nothing for demo/necro. Same for Tarantia Noble Arena.