I had problems again and did more research into it, found out that actually it has more to do with cpu frequency then irq. If cpu governor is set to constant freq value, even lowest 480Mhz, then I have no problem with wireless throughput going to max value very quickly. With default ondemand scaling throughput goes to max slowly, sometimes it never goes to max and ssh terminal lags during speed test. Also %cpu/%irq values jump to 10-30% with ondemand scaling but with constant freq its solid below 10% during speed test.