Well Baz,
In all the years I have used multi-fly leaders for trout, I can hardly remember getting hooked up, even when the fish is taken on the top dropper.
I have of course on occasions hooked two trout at once, and released both of them quite safely too.
I would never use a multi-fly leader where the trout run very big or where there are snags. Even soo, trout, compared with coarse fish do tend to fight in the open and not run for snags.
In SA there are some truly barbaric two hook rigs used for carp. Many of them are designed to hook the carp in the mouth, and in the head at the same time. But to be fair, carp caught like this are going to be clonked anyway.