Using an Omnitik in my Office I get only 33-35MBit down 50-60MBit up.
I would have expected at least 80-90MBit/s. 802.11n/40MHz Channel/2 Channels.

My Laptop has an Intel N7260 Chipset. Data Rate in connection table is 300MBit/s.

/interface wireless
set [ find default-name=wlan1 ] antenna-gain=7 band=5ghz-a/n bridge-mode=\
disabled channel-width=20/40mhz-ht-above country=germany disabled=no \
frequency=5260 frequency-mode=regulatory-domain hw-retries=15 l2mtu=2290 \
mac-address=00:0C:42:C2:C3:18 mode=ap-bridge radio-name=OT1 \
security-profile=xy wireless-protocol=802.11

What is normal for a omnitik?

For better result, try to set the power output lower.

The performance from the omnitik depends from many things.