Yeeehhaaw! Thanks to this great guide, i successfully de-bricked my 2TB "My Book" without losing a single bit of my files. THANK YOU ALL!
My device suddenly died after a short power outage, i waited for hours and even days but the LED at the front stays yellow and doesn't become green.
Having a software-raid on a device without a defined shutdown procedure (even without a power switch) is a bad idea, IMHO. Linux md-raids often have problems when they are not properly stopped. I think that was the problem in my case.
I also found out that you cannot mount the ext4-Partition directly (because of the 64k block size) to recover data, but debugfs can! Before i followed the instructions above, i made a complete backup of the DataVolume-Directory, using debugfs and the rdump command on a Ubuntu-Box. I connected the hard-disk with a simple USB-to-SATA adapter.