Dragons are nice, but the towers are resistant to fire damage. This is why I didn't recommend them. On normal, it won't be much of a problem, but on imposiible, it is, because the towers have 12-15k points.
As for believing, every screen you need is in these threads:
http://forum.1cpublishing.eu/showthread.php?t=11194
http://forum.1cpublishing.eu/showpos...1&postcount=67
as well as a save game to show everything is clean
It is all about knowing the game mechanics, the boss behaviour and knowing how to use it to your advantage.