I think this one is quite up for debate. Though his actual FG% has gone down, his TS% (True Shooting, which is a measure of points scored per shot taken, and takes into account attempts on which a player was fouled and does not get a FGA) has been fantastic. His career TS% is #13 all-time in the combined NBA/ABA, as a point of reference, and last year he was only a hint below his career. This year he's a bit lower than that (in a 5-game sample) but this year's TS% would still be good for #50 all time. He's a very efficient shooter even when you do take into account shots on which he was fouled. It's his defense that appears to be the issue to me.
I think the Tyreke emerging and others like JT, Beno, Noc, and Casspi starting to be threats offensively will help Martin out when he comes back. I think this is especially true of Tyreke and JT who have shown that they can consistently draw double-teams (or triple-teams in Evan's case).