Problem FTB Infinity server lagging, low tps

[Pentacore]

• What OS are you running?
  Windows Server 2012 R2 Standard 64-bit
• Are you using minecraft hosting provider or a dedicated/local server not designed for minecraft?
  Dedicated server at home
• What version of FTB are you using? (Dont just say latest tell us the version)
  FTB Infinity Evolved 2.5.0
• Did you add any mods to the server pack?
  Veinminer, Sampler and better building wands
• What are your server specs?
  2x Intel Xeon E5450 @ 3.00GHz
  16,0GB FB-DDR2 EEC
  512MB NVIDIA GeForce GTS 250
  Server running on a 1TB SSHD
• A good detailed paragraph about the problem
  The server is very laggy with huge delays and low tps (1.7 avg tps 9% severe lagg).
  
  Server arguments:
  java -server -Xms512M -Xmx6G -XXermSize=512M -XX:+UseParNewGC -XX:+CMSIncrementalPacing -XX:+CMSClassUnloadingEnabled -XXarallelGCThreads=3 -XX:MinHeapFreeRatio=5 -XX:MaxHeapFreeRatio=10 -jar FTBServer-1.7.10-1614.jar nogui
  
  The amount of players doesnt seem to matter and the TPS of 1.7 is when i alone is standing in the middle of nowhere, CPU usage is low (all cores working at below 10%) and memory usage stays at around 2-3GB, The server restarts every 4th hour and the lagg is present at startup.
  
  Done checks on the SSHD and RAM without any problems.