As I pointed out in last month's CTDWAT, McLemore has the same number of 20+ point games that he had in his last season in Sacramento (or, actually, any one of his seasons in Sacramento, aside from his second one), but is somehow averaging fewer points. That means that he's just swinging from decent to terrible, with no stops in-between.
I tell you what though, he does appear to definitely benefit from playing with two ball-dominant guys, who are going to do all his thinking for him. Also, the fact that Gordon is injured means that there is no legitimate challenger for his spot, so he's not looking over his shoulder all the time. He gets to play free and loose in Houston; anything they get out of him offensively is "found money," so he doesn't have the burden of 'needing' to score X amount of points for his team to win, any more.
In Houston, if McLemore scores 20, they're going to win by 30, and if he scores zero, they're still going to win by 10. In Sacramento, when McLemore scored zero, the Kings usually lost by 10.