This is an aggravating subject for me, and I have posted about it before.
If you really want to pull some hair, buy a good quality power meter that checks the power out straight from the card. We have a Berkeley Varitronics Systems Wi-Fi Power Analyzer called a Caterpillar. It is worth the money because you start to see what is REALLY coming out of the radios.
We have numerous cards on default power levels that put out far less than the cards rate, but if you ask about this, you are told never to manually set the cards rates, as you could burn the radio up (how can it burn a card up to put out the full power it is rated for?).
I'm going to flat out say that I'm NOT REFEREEING TO MIKROTIK here, but other manufactures are selling equipment that says it is putting out, say 24 dBm, when in fact it is putting out less than half of that. We busted someone just today doing that exact same thing...and they flat out admitted the literature for the card was not correct. If we had not had the analyzer, we wouldn't have known.
But it is frustrating with Mikrotik as well, because some cards just put out the right power right out of the shrink wrap (our last XR2's did), and others do not.
And if you do not have a power analyzer, you will never know.
At some point, we thought our Analyzer was off, but when it says the output is low, the APs do not get the range they should, so I think it is right. It is also my personal opinion that people have paid extra money for high-powered cards, and did not get anywhere close to what they should have out of those cards.
What I wish is if more people would spend the money for the power analyzers...because then more people might be getting vocal about this issue...
Just my two cents.