There's a very simple explanation to that and it only requires going beyond the simple minds that we tend to resort to because, let's face it, we don't like the player we speak of.
Anyway, the simple explanation is that, Lendl's appointment had never anything to do with Masters as Murray, by that time, had won many of those. Therefore, Lendl's appointment had everything to do with winning his first Slam and possibly Wimbledon. So the main focus had always been winning the first Slam and never Masters.
As to consistency, again, consistency wasn't the main deal here but winning the first Slam. Andy has been very consistent with or without Lendl in Majors, that is, if we take time and care to notice. So that again wasn't the issue. The issue had always been winning his first Slam that he failed to do despite making the finals a few times. He had absolutely no other reasons to hire Lendl other than to help him win his first Slam. You need to take a look at the priorities he had in place at that time and what he had achieved by that time already and you will find the answer there.
Even still, Andy doesn't need to be highly consistent - certainly not as consistent as either Federer or Nole (two of the most consistent players of this era in my opinion) - as long as he focuses on to win more Majors. His priorities are very different than the others and will always be, so his consistency will be directly related to that. Rest assured, he'll be very consistent in Majors where things matter the most - for him anyway.
Is post Lendl Murray better? Yes, of course. He has now 2 Slams behind him and a few more to come. The mental obstacle he always had in Slam finals are now long gone. The only task he has now ahead of him is to deal with Nadal in a Major and it may come at the expense of another Major, but as long as he takes care of it, it will free him forever. And he will achieve what he wants.
