I'm looking for something fairly simple to install, that will monitor network traffic on the vswitch for my esxi node as we're getting ddosed and I need to be able to easily see where the traffic is coming from.
On the actual vSwitch? Well you can't as far as I know that's a limitation of the in-built vSwitch, you can with Cisco's Nexus V1000 alternative virtual switch replacement but not with the regular one.
To be honest you should really be dealing with things like DOS issues before it hits your ESX boxes, via a router/firewall/LB etc. These will obviously let you deal with their own interfaces and help you finding out where your DOS is coming from.
If the DOS is internally-sourced (i.e. one VM attacking another) then again you should be able to use the VM's own OS tool set to find that out. The in-built vSwitch does provide some diagnostics/metrics but not that many, even with the next version of code.