If you're putting together a coffer key party (or able to solo these), these are good for skilling up between about 165-200. As a 62RDM, I was able to kill the Even Matches, but even with decent +acc gear I missed A LOT. Still, I managed to raise my dagger skill ten levels in about an hour, which is pretty decent.
The only real problem with attempting to skill on these is that everyone and their dog comes down here and kills them. More often than not, you'll find an empty room and a level 75 character looking pleased with themselves.
We got 3 keys off 4 kills. We had a Thief in our team though. These guys seem to have the highest drop rate for coffer keys, problem is there are a bunch of other lower lvl undead around them who have dismal drop rates that you have to clear first to reach these weapons.
They're a room loaded with these guys near the room where Serker pops. There's also a Tainted Meat in the back though, so you gotta be careful...these got great drop rates, but Tainted Meat is better (much less effecient since there's only 2 or 3 in all of Garlaige though)