Firstly i have quite a few (25+) of 2820/2830 deployed and have been overall very happy with these products for their price point.
However we are seeing issues now with throughput of these devices on new faster connections ( BT Infinity FTTC and Virgin Media 60+)

I have done extensive testing and certainly would not expect a Home Hub 3/TP-LINK £40/Super hub router to provide more throughput than a brand new 2830n (sb) with latest firmware 3.3.7 but this is the case. Anyone else seeing this issue ?
Yes QOS is off so not related to that !
I have tried many configs and conclude i am going to have a look at other products for my clients + myself.

eg. Virgin media 60MB with TP-Link i get an average of 53Mbps / 3Mbps and with Daytek only 34Mbps / 2.5 Mbps
BT Infinity with HH3 get an average 37Mbps / 8 Mbps and with Draytek only 31 Mbps / 5 Mbps.

I know that 2820 has a lower throughput than 2830 but i have replaced many of the 2820 lately with 2830.
This does not bode well and will mean a refresh of many of my gateways,

update : I realise that both models of routers do have a max of 50Mbps firewall throughput but i am just not even getting that.
Shame they do not handle more throughput ;-(

I have currently got an open support call with Draytek UK in regards to WAN2 speeds,

According to specifications, WAN2 speed is rated up to 90Mbs for 2830.
Using JDautospeedtester (http://www.gmwsoftware.co.uk) for my speed tests (great tool for repeated speedtests) I have found that having WIFI enabled (with or without clients connected) immediately limits measured WAN2 speeds to <25Mbs or even lower.

With WIFI disabled, my Virgin Media 60Mbs (SuperHub in modem mode) service hits upto 64Mbs measured download speeds even with CSM, URL and Firewall enabled on the 2830n. You enable WIFI and top speeds is less than half.

My router is the 2830n single band running latest 3.7.7 firmware available from Draytek UK.
Currently I'm using an old BT Home HUB with DHCP disabled as a simple WIFI access point connected to my 2830n pending outcome of my outstanding call with Draytek UK.

Maybe you or indeed other forum members could repeat this simple test on the 2830n models to check if this a design / firmware fault with this Draytek model.

========= update ==============

After further troubleshooting, it was the build-in NIC on my HP desktop that was faulty. Strange that this caused the odd behaviour with the wifi speeds.

I can confirm that with fault free LAN, the 2830n is happy to fully support my WAN2 speeds (up to 65Mbs) with and without Firewall / Content filtering enabled.

I have a 2830n on FTTP (100Mb down/15Mb up), I have saturated the link a couple of times. Doesn't seem to be a problem for me.