This seems like a strange line of logic to me, as it's Hamilton that has been dropping points due to bad luck. He lost second position in Australia to the safety car, in , he lost multiple positions in Malaysia to a bad pit stop, and took a 5 place grid penalty in China again through no fault of his own.
I think Button can lead LH if he sorts out his qualifying, but if things remain as they have done so far, I dont see it.
two front row starts out of three, and you think quali needs "sorting out"
By the same logic that you applied above JB could have won every race so far (his mistake in Malaysia will over taking a back marker while in the lead, and a disappointing 2nd place after a botched pitstop)
I cant see how many can logically argue that LH has proven better race pace so far this season - if anything its exactly the opposite (who cares where JB qualifies as long as the McLaren position is maximized , which it has been in 2 out of three weekends so far - in qualifying)
The expected higher temps in Bahrain should suit McLaren better (as long as its not too hot, as I believe the new tyres have a narrower operating temp than last season) , so their qualifying should be better in general. It was widely claimed that no one did a better lap in the "cooler" 2nd run in final quali in China, so it was a great pity JB didnt prove directly how fast he was against LH by mucking up Q2 a little (again this happened because of cooler track temps, so it shouldnt happen again anyway)