1) It occasionally leaks because the hot end is inside PTFE instead of the PTFE being inside the hot end. This idea is inspired by Nophead's plumbstruder post and Adrian's geared extruder nozzle.
2) Don't use glue.
3) Don't use brittle nichrome wire. Even Makerbot has stopped using nichrome wire in their latest MK5 design.
4) I don't have much room to work with in the current Mendel design.
So, what I've decided to do is completely redesign the xcarriage. This will give me more room. Also, I will completely redesign the extruder so that it doesn't use glue or nichrome while incorporating the PTFE update.
I am attaching some OpenSCAD renders of what I am thinking of making. I won't have all the materials for a few days, so if anyone has feedback on the design I still have time to change it before I pull out my lathe, taps, and my backup Darwin printer. Drop me a line or leave a comment. Otherwise, be prepared to learn from my mistakes yet again. Ha.