Yep,
hermit crabs by a large should be left out of reef tanks. At the very least, their numbers should be far fewer than what has been recommended in the past. They will clean the rock until your "live" rock is nothing but bacteria and coraline. I have a couple just because I like them, but only 2 small individuals for my 150 gallon tank. At this density, they have little impact.
The odd thing about my blue was that he was eating nassarius snails less than 1/2 his size. Will red legs and zebras do this too? If so I can double or triple the snails and take the hermits back (all but one that I really really like)
I had Scarlets in my old tank. Never witnessed any carnivore action except on dead stuff. But, that's not saying they weren't plucking fan worms though.
But, all in all I was happier with Scarlets than with Blue-legs from an even older tank. But, now I'm just running snails. The Nassarius do the same thing as hermits and eat dead stuff and rotting food and aren't fan worm eaters. But, you need some sand.