The old Scott Addams text adventures(among others) utilized two word phrases(such as go south, climb tree) and these were difficult to say the least. Having a phrasing system that holds three and four words can be nigh impossible(unless you get lucky).
For the preservation of the current system, the key word system seems to fit best. Since there are several words that would fit, you could require getting the right word. The name of npc, name of item wanted, or giving the item required would make the quest as difficult as any side quest could be. I would even applaud a system where the phrasing takes a certain grammar structure(such as npc wants item or i want item). The confusion from the current system comes from MPCs responding to phrases with different structures. \"Give me a quest\" and \"NPC wants item\" are two different grammar structures. If it was \"Give me (Thing wanted here)\" or \"I want (thing)\"/\"NPC wants (thing)\", the quests would be at a more appropriate level.
It is an alpha test. I am sure they are working on an appropriate solution.
Kythag