How can I optimize Wifi latency?

[tve]

I'm trying to program an arduino over wifi using an ESP8266 as a transparent TCP/Wifi to UART bridge. The problem I'm running into is that the round-trip latency from the programmer sending a block to the arduino until it receives the ACK back from the arduino is too long. Looking at tcpdump, it looks like it takes ~400ms for the ESP to respond to any TCP data. I can see from looking at the serial lines that it's not the arduino's fault. Is this typical? Can I optimize this somehow?
I'm using the SDK-0.9.5 and a custom user_main, compiled with esp-open-sdk, running in STA+AP mode on a WPA2 wifi network.