I don't think it's a great idea to start trying to get through to the room assigners. They have plenty of work already. For heaven's sake...because of these, and other, boards, they stopped accepting faxes at a lot of the resorts. They were just innundated with faxed requests. Just give your requests when you make your reservation. If you didn't, for some reason, then call back and have them added now. You should be able to get your requests added up to about 5 days before you arrive. The rooms start getting blocked out a week, or a bit less, before you arrive.
As for how to get your requests met.....simple, keep it simple. If you ask for, let's say at the Polynesian, a third floor room in Tokelau that faces towards the lagoon...well you have just narrowed your room availability to about 4 rooms. So, I would ask for a more general location....Tokelau, with a balcony. Then, let the pieces fall where they may.
After all, you aren't buying the room, only going to be there for a week or so.
There truly aren't rooms that are horrible....well, maybe one or two, but I wouldn't worry all that much about getting one.