You can easily optimize the protection capabilities of your FortiGate with the FortiGuard Enterprise Bundle. This

Advanced Threat Protection (IPS, Advanced Malware Protection Service, Application Control, and FortiCare Premium)

Specifications:

But, there is certainly nothing (even with the 30E) that will prevent you getting that speed reliably if you have it correctly configured. It will be a config issue and certainly not a bug or Fortinet defect. These basic configs work well on Fortigates and are well validated and tested. But it may take time to work through it. FWF_30E-v6-build0302-FORTINET.out – FortiWifi build – Normal FortiGate + 2.4/5 Ghz radios for A/B/G/N wireless. Serial number starts with: FWF30E Because your WAN interface is currently only 100Mb/s you will never get more internet speed than that.

Unified Threat Protection (UTP) (IPS, Advanced Malware Protection, Application Control, Web & Video Filtering, Antispam Service, and FortiCare Premium)

Enterprise Bundle

High performance UTM - firewall, VPN, IPS, application control, web filtering, antivirus, antispam, DLP and more