Wonders will never cease!
You're not going to believe this: I have a TF101 with KitKass 4.4.4.
Until you told me to wipe data I never wiped it, not because I didn't want to but because it never happened (ignorance, sloppiness, or whatever; I also vaguely recall seeing a screen message saying that it wouldn't be wiped and thought it had to be left alone).
Of course I had read Fedrico's guide but gave up as as soon as I saw "it requires root" - didn't know how to find out or implement this due to the bootloop.
After the first bootloop I thought EasyFlasher would handle things better, but you're right: this and my other attempts just made things worse.
So this morning I wiped cache, dalvik, data, and rebooted: BINGO (or rather KatKiss)!
Here is a screen image (I hope), don't worry if you can't read the Dutch text on it:
Attachment 8080
If you want further details, please let me know either in this forum or - if you want to try Skype - via a private message.
This has been my first foray into the world of Android "updgrades" and I still have a lot to learn if I ever have to do this again; you know I'm an Android user, not a developer.
Let me repeat what I have said before: thank you very much for your help.