I have to echo SQLRNNR here. The queries are taking a long time for not many rows, but of course row count is not necessarily an indicator of complexity.

Optimising the queries could be solved by faster T-SQL, for example if there are slow parts that are not optimised for set-based logic. It might be that when the report queries were first created that your DW was much smaller and they ran fine, but they haven't scaled well as your DW has grown. It might be that you need good indexes or better indexes if you have them already. It might be that the queries can't make use of the indexes because of the way they are written.

If all the report queries are written in a similar style then you might benefit from taking the slowest one and getting some advice on it and then optimising the rest of them in order of slowness. If it's a huge amount of work then you might even benefit from getting in a specialist to help.

The conclusion is that you won't benefit from moving SSRS to another server because the queries are still going to run on the DW database engine.