I think the divers see big lings because most of the time they are diving in the winter when lings are shallow gruading egg. Back in the early 90' as a kid I can remeber drift down chanel where they spawn and getting +10lb every drop in less than 70' of water. I would never do that today, it is very bad to take them off there eggs even for couple minutes. You can usually scare up some big ones in late May after they are done spawning and are hungery... that is when they go shallow for greenlings, rock fish and small lings (You can't keep them until June, if retention is allowed in your area). During the summer when drift fishing (buzz bombing) for salmon I will usually get one 7 to 10 lb with all the little guys every other day. But the only big ones, +10lb, in the summer are almost always caught on very steep drop off (180' to say 80' in less than 100') where a back eddy is. I don't fish for them specifically any more but since I love to drift fish for salmon I aways get a few.
I don't like fishing deeper than 120' drifting either as rock fish will have their swim blatter expand (lings, salmon, flounder, dogfish don't for they can out gas quickly). I have heard poking a whole in it will let them swim down again but who knows how long they live after. If you know you have rockfish you are not going to keep and it coming up from deep than 80' stop a couple times on the way up for 5-10 second, this will help the fish decompress. It does work and can keep them from being eagle food.
Now, I know I'm begining to semonizes but if you take some kid out to bottom fish jsut for the fun of fishing with out keeping fish shallow. There are a lot more little lings at 60' and up and they are really aggressive and you won't kill any rockfish if they are brought up to quick.
Have fun, Jason