The linked SERVER tickets are fixed in WiredTiger release 2.5.3
rc10/wiredTiger multi collection/DB bulk insert slow than rc8 in initial insertion phase
Extended pauses in WiredTiger when workers greatly exceeds number of cores
WiredTiger uses substantially more memory than accounted for by cache
mongod fatal assertion after "hazard pointer table full" message
Got signal: 11 (Segmentation fault).
WiredTiger unable to start if crash leaves 0-length WiredTiger file
Unable to start mongod after unclean shutdown