How about:
Until you have marked a drama as complete, you can only rate/review individual episodes. So to the person who was saying that they rate as they go so if a drama is on hold they have a marker for why it is on hold, what if until the drama is marked as complete there's some kind of average score of all the episodes you've rated. Once you've marked the drama as complete, you can rate and review the drama as a whole.
For dropped dramas, is there a way for some kind of drop down field that asks at which episode and why the drama was dropped - from an agreed list (maybe poll users for the reasons they drop dramas - bad acting, over the top plot etc). there could then be some kind of list of the top 3 reasons a drama was dropped and the average dropping episode. I know i'm taking this much further than the original post, and it would be a lot of work. It's something that I've been thinking about a lot.
Also how about some kind of tally of the number of people who have marked a drama complete versus the number who have it on hold and the number who have dropped it. it would give some kind of context to the rating maybe?