Is it really necessary to poach the salmon in advance of assembling the cakes? On reading, it occurred to me this might render them a little o...

You don't have to poach the salmon first, but you will end up with a much different texture in the final cake. I have done this using a food processor to grind the raw salmon and then binding it with about 1 egg white per 1.5# salmon. It will result in a "burger" kind of texture. Also, you will have to cook the cakes longer to make sure they're cooked in the center instead of just warming/crisping them.

That's a really interesting question, and I'd have to say, I've honestly never tried. I've never found that the poaching makes the salmon cakes dry, unless you over cook the salmon in cooking. You only sautee them long enough to heat them through and get them to hang together since there's nothing raw in the cakes at that point. If you wanted to use raw salmon, I'd imagine you'd have to very finely chop it, and you may need to use egg as a binder rather than mayonnaise and potentially change the proportions somewhat and refrigerate (or freeze) them longer to make sure they hold together. But, you should give it a try if you want! I'd love to hear how it goes.