Expecting terminal programs to interact sanely with mouse gestures is somewhat futile. If I need to paste something from a vim buffer into a graphical application, I use :'<,'>!xsel -bi to copy the text. If I were doing it more often, I would probably add a keybinding to streamline the process, and solve minor annoyances like having to undo to get the copied lines back. Maybe there is a good plugin for clipboard integration?