You just diagnosed the problem, the lack of an organising half. Dylan Brown is not an organiser. He's more a ball runner. Yes, he may be all that's available, however does that mean he's the right fit for what is needed? In my opinion, no. Have a look at the Roosters, needed a hooker so they signed Brandon Smith and look how that worked out. He didn't fit what the side needed, so now they are looking to get rid of him.
Sometimes sitting pat can be a better long term move than going out and signing the only available "big name" at a position of need on a long term deal. O'Sullivan is good at what he does, but that doesn't mean he's perfect either.