I was comparing couple different router with wireless chips used in STA mode, which includes chips supported by mwlwifi, mwl8k, ath9k and ath10k, I found that:
AR9344 - ath9k: 100mbps ~ 80% SIRQ
QCA9558 - ath10k: 100mbps ~55% SIRQ
88F6282 - mwl8k: 35 mbps ~99% SIRQ
MV78230 - mwlwifi: 100mbps ~47% SIRQ (one core maxed out basically)
Supposedly both 88F6282 and MV78230 are quite a lot more powerful than ar9344 and qca9558. But mwl8k and mwlwifi drivers seems to have performance issue in STA mode. Does this wireless handling reside in the firmware blob? The mwl8k driver also doesn't seem to suffer from the same problem in AP mode, which can easily attain 100mbps.