@saddleback, problem with WDS links is that those still havent been generalised by the vendors. So the style for building up the WDS link with engenius devices can be (slightly) different compared to other brands. That is why all vendors, including EnGenius, recommend to always create WDS links between same brands, and if possible, use the same models. Or at least with the exact same chipsets.
for client bridge, it is normal for this behavior. That is where the big difference is located between client bridge(CB) and wds station.
CB mode was developed to work as a legacy solution, so you can connect a wired-only device, to your wireless network. Actually, the CB device can be compared to an oversized WLAN Adapter. what is the feedback that you get when running ping tests from the device behind the client bridge to your main router?
just to clarify, both access point and connected client are using different IP addresses, but are registered with the same MAC address?
If so, which firmware are you currently running on your ENH500? 1.5.6? or 1.5.74?