The crash log can be found here:
http://pastebin.com/6tDRNCUZ
It looks like the crash is from blood magic, probably partially due to that removal. One of the blocks in the ritual is bugged out and crashing the server.
You have a few options :
1) Download MCEdit and open the world. Locate the block/blocks (according to the crash, its at (-414,179,-1367), and delete it.
2) Use MCEdit, and delete the entire chunk or chunks the ritual was being performed in. According to the crash : (at 2,11,9 in -26,-86; contains blocks -416,0,-1376 to -401,255,-1361) (I'm not sure exactly how to parse chunk location/numbering, unfortunately). DOWNSIDE : This will delete everything in the chunks deleted.
3) Disable Blood Magic, load the world, have someone log into the area, then stop the server and re-enable it again. DOWNSIDE is that all blood magic stuff will be removed from the world.
3) Can I keep the region files (given that there appears to be no backup system in place)
I left Aroma Backup out of the server files, feeling that most server owners have their own backup systems they prefer to use, and could install AromaBackup themselves if needed. In future Server zips, I'll include Aroma Backup as well.