RT-AC87U Higher Latency than Netgear WNDR400 in Games

[Wolperdinger]

I recently replaced my Netgear WNDR4000 with an RT-AC87U. My son and I play a lot of games, mostly World of Tanks. He uses a direct wired connection to the router, and I use 2.4Ghz wireless. We were both getting pings of 25-45ms with the WNDR4000. With the RT-AC87U, we were disappointed to find that our latency had increased to 100-120ms. Certainly not unplayable, but the difference is noticeable in some cases. The increase is the same on the wired and the wireless connections. I've tried replacing the Asus firmware with the Merlin firmware, but no change. I've mucked about with various settings, but have not been able to get the latency down. Any suggestions would be greatly appreciated!