master-interface=wlan2 name=wlan3
Repeater mode on the same wireless radio (wlan2) , will at least reduce the throughput to 1/2. (receive, send) for every packet.
WLAN interfaces are known to be inefficient at high speeds. (Their AMPDU aggregation is limited to 3895 bytes per MPDU, and A-MPDU to 262000 bytes) This means many wifi access attempts (contention delays) to transmit a large file http://forum.mikrotik.com/t/wifiwave2-expected-performance/160075/3
At least make sure the A-MPDU tick-mark is set. (By default only set for priority 0). See http://forum.mikrotik.com/t/help-mikrotik-capsman-wireless-download-speed-max-200mb-but-pcs-mobiles-link-speed-is-866mbps/142677/1
So having 1/4 of the speed is no surprise. “wifiwave2” has big buffer sizes, so much less frequent overhead before transmitting. And the repeater function at least halves the “wlan” performance.