Upgraded Aerohive AP
That seems like an appropriate device to AP ratio at 20.46 devices per AP however if you are experiencing degraded performance on the wireless then you need to look at a number of things. First it's important to note that the 20-30 devices per AP is really more a theoretical limit rather than a hard and fast limit. For example I could only have 10 devices associated to one AP but if they are all trying to stream 1080p video at the same time that could definitely push the physical limits of the AP. Second you also need to look at signal strength. One really nice thing about the 350's is that they have external antenna's so that you can better shape the coverage area of each AP where necessary.