Having a similar issue, since updating to 7.6.1 I have had multiple dropouts and connection issues with the wireless.
My speed is not the best on ADSL2 anyway (I am in Australia, crap internet at the best of times).
I was getting 4.87mbit with 7.6 now 0.7mbit with 7.6.1. I rolled back to 7.5 adn I am back to 4.8mbit.
Spoke to Apple care and I have been advised to update again and send screen shots....what a hassle.
Also noticed that the new Air Port Utility 6.0 deletes and also does not give the ability to roll back Firmware versions like 5.6 did.
You can download Airport Utility 5.6 that you can use instead of Airport Utility 6.0
5.6 has logs etc., just like the prior 5.3 version
This way you can view your logs and see what is going on.