I've been using lots of big worms lately. I use ol monster, even magnum a little bit.
I use owner's twist lock light wire in size 6/0 for ol monster. Even if it is light wire, they change the size of wire accordingly, so with 6/0 I feel they are strong enough. I set hook depending on how the bite is. It is kinda hard to explain the timing of setting the hook, because it is case by case, but if I try to put it in words, If it is hard bites, like strong pull, I set hook immediately. If it is a very slight tick, I'll give just a couple of a few seconds of delay. My hook up ratio is pretty good, must be over 90%.
But if it was working before and suddenly missing, as other poster mentioned, there might be smaller fish nibbling. I would switch out to shorter bait and nail the fish to find out.