Extra Attack

I'd say you're reading too much into it.

I'd look at it like

Speed - ok, I'm not so fast anymore, my dex is hindered somehow. less defensive and offensive. Sucks!

Extra attack - I'm losing one attack per round, my h2h is better than anyone, this is not a good idea.

For b|ms? This is a matter of debate. Not tooting my own horn, but I'd like to think Brothem did fairly well. If not VERY well. I wore 4 pieces of encumbering armor all the time and never was at a disadvantage. With max anats and a certain combo of race/cabal...it just made alot of the blademaster key skills not even worth it.

Extra attack is for monks, if you were to encumber both your advanced and basic martial arts skills but not extra attack you would get two attacks per round.

At least that is what I recall, been quite a while since I played a monk.