Only you will be able to judge if the splice has caused any drop in the speed/quality of your connection.
The join should be suitably protected from the elements if it is intended to be a permanent arrangement. Splitting the cable in that way is sometimes done as a 'get-you-working' measure to reconnect a customer with a cable fault until a new cable is installed. Often the new cable never happens.
Post up some pic's of how the cable splice has been left which might result in someone being sent back to remedy it if it is unsuitable for long tem reliability.