I agree if its not broke don't fix it. Ratings and audiences were finding both series in the UK. Now everything is going to get effed up!
Merlin is a conundrum of a little show. The first half of a season is always the same old and fairly kiddie and crappy, then the second half of the series is dark, brooding, heavy, and in high gear. I can't believe they are being shortened to 10 eps when I've been wishing for more two part or supersized tv movie type episodes. Perhaps a two hour special movie event to tide folks over would be nice.
Otherwise, I think this move is going to hurt both shows. If viewers don't like the tract DW is taking, fans will complain, and the short attention span youth they've been chasing for Merlin will forget all about it and move on to something else.
Another reason this is kind of bad, won't the new Starz Camelot and Game of Thrones be out now in Merlin's place? Sure, take a bye week while your competition revs up! Dumbass move. Why not be really daring and show Merlin in the autum on BBC America. You know, the channel that shows American movies with British people in them. (Seriously is that their new slogan?)