What did I do wrong? Slow cooker.

I finally got a chance to use my new slow cooker for the first time tonight (YAY!!) and I thought I'd start off simply. I did a topside roast beef (1.5kg) in a gravy/soup liquid (2 cups) and cooked it for 7 hours like the receipe said too. When I got it out it pulled apart easily but was dry.
I don't understand what I did wrong. Any advice/tips/help?

On a side note does the piece of meat I'm cooking have to be completely covered in juices/gravy or can some be sticking out?

Sorry for the questions but the instruction manual I got with it is useless!!

TIA,
Dan.

I'm no expert but we pull the meat apart in the cooker an hour or two before it's done, just so it can soak up more juices... Works for us.

i find it works a lot better if the liquid completely covers the meat. O often have to add more than the recipe calls for becuase I have a 6L slow cooker