i have a mikrotik AP composed of rb333 350mw card and an omni 12dbi antenna.i have clients using nanostation5.
from customer site to AP is about 1km clear line of sight.
but when am at customers site and ping the AP the pings go up to 1300ms.form AP the ping are also.
my AP is running on frequency 5320.

Here is a list to check into high pings are mostly do to resends

Interference: try different channels.
Hidden node issue: depending on # of clients, often the problem shows up around 10 or more clients, to correct use RTS/CTS... info is documented in the forum.
If only one client is affected, likely bad multi path: adjust location/height of client antenna