Theres a addon called PassLoot wich auto-selects pass/need/greed according to preset lists of rules.
It has a pretty amazing list of possible criterias, like: numer of loots (handy for bagspace), "color" of item (all green/blue BoP to disenchanter), itemLevel, BoP/BoE, type of item (1hand blunt, 2 hand blunt, mail armor, alchemy recepie, quest, the list is Long of all the subcategories).

With my setup I only roll manually on blues/epics, that one of my toons might want to use. Too low itemLevel, and its considered junk for disenchanting.

It does not auto-disenchant tho, just rolls as pre-decided in the lists.
..and remember that the lists runs from top to bottom, if you want to give it a try. anything Not caught in pass/greed/need is still manually rolled. ..and you can de-select the pass/greed/need checkboxes for temporarely disabling the rule.