I'd hate them if they were that long too, and anyone taking 30 minutes to do a boss guide is probably doing something wrong.
That being said, it's rare that I see long guides for fights in this game, with the longest I can remember being Mizteq's Turn 9 guide just from the sheer amount of things that have to be done in that fight, and that clocked in at 18 minutes.
For text guides, I'd love to see the kind of effort put into stuff like this
http://midnightinsomnia.com/ravana/ more often. Clear and concise writing with video, gifs, or diagrams where necessary, and the ability to narrow it down based on role.