Well Mefisto usually wanted the last 15 lines when a crash or bug occured, so 25 should be more than enough. It would surely cost less HDD space and write time (which makes the PC slow usually) I'll doubt it that DKFX can cause a 100% CPU load on modern systems. If it does than that's a possible bug too I guess.
Edit:
Ok, I just ran the Debug version with the Taskmanager on the other screen (gotta love 2!) it does pull 100% cpu (well 1 of 4) so that can also cause the lack in performance. The memory doesn't go beyond 34MB. So I think a bug snuck in somewhere compared to the older versions. A 14 year old game that can get a Core 2 Quad on it's knees surely has a bug somewhere. :P