Hey, I was in the exact same position as you last year. I got offered Liberty Dock and I was gutted about the distance etc too. But here is my HONEST opinion.
Firstly, it isn't that bad at all. As for the distance, it is no way a 50 minute walk. Once you know the route, it'll take about 35 minutes if you're strolling. And there is a great bus route, it's from right outside the halls to right outside the university and that takes about 30 minutes on an average day. It's actually in a good location aside from that, like a 10 minute walk to the bus station and about a 5 minute car ride to the train station, again there are direct buses to take you there which aren't long at all. The town centre is really nearby and it makes it really easy to walk to and from certain clubs. The area is mega pretty & I honestly really loved it as I settled in.
As for the comment about it being split between 3 universities, I honestly never met a person from anywhere other than uni of Leeds. And I knew a lot of people. They try and group you together with people in your university and it is mostly uni of students. And even if you are paired with someone not from your university, the majority of your block will be at uni of. trust me. Don't let the distance put you off. It's not that bad. You just hop on the 28 bus right outside of uni and in half an hour you'll get to the front of Liberty Dock, and that's only because of the amount of stops it does. If you get a taxi, it takes just under 10 minutes, which isn't far at all.
If you have anymore questions, feel free to ask me! But I'm even considering moving back to this accommodation after my second year is done, don't let it put you off!