EDIT;; This patch really wasn't meant to be, eh Riot?
http://na.leagueoflegends.com/board/showthread.php?t=2244698
If you ever want to truly get into Dominion, READ THIS.
It's absurdly comprehensive, to say the least.
Meh, I have a few issues with it. It's very well written, but it's a guide geared towards high elo. Nothing wrong with that, but there's some things that aren't addressed for lower elos. I'm a middle of the pack elo in Dominion with a positive win-loss ratio btw.
#1: I'm really iffy about concrete roles in Dominion. You should be looking for champion synergy rather than you need A and B like in SR. I especially do not think that ranged AD carries are required, insofar in that you simply need poke. The sample team comp seems too squishy for my taste.
#2: This needs to be stressed: Shaco should always, always be banned in lower elos. He limits your entire's team mobility by picking at them in the jungle and low elo people simply do not understand how to deal with him or even attempt to limit their time in the jungle while he's around. Teemo can do the same thing, but Shaco also has an escape that makes dueling him hell and is one of the better if not best defenders. If he's not banned, you better first pick him.
#3: Some supports in lower elos aren't a good choice, such as Janna and Sona. Soraka is a bot laner and should not be played in her usual role. Lower elo people play them too passively and more often than not find themselves unable to deal with threats because all they do is support. Tanky champs that provide CC and initiation such as Leona and Rammus are king though, as is Blitz.
#4: Summoner spells: I really want to say that Exhaust is a bit like Flash in SR. It is honestly the bread and butter default spell I take on nearly every champ. It will help you win duels, save points, and win teamfights, especially since Cleanse is rare. Revive isn't great in lower elos for two reasons: I've often seen that in solo queue, bot is decided like 15 seconds before the game starts, and the cooldown is incredibly long. In lower elos, this should be taken with a disclaimer. I know, I'm one of the awful people who uses Ghost, but Ghost really helps with saving points quickly if you're partially across the map.
He doesn't go over specific strong picks, but seeing any of the following makes me a happy camper: Ez, Jax, Panth, Amumu, Malz, Shen. Obviously these aren't all of the best picks, but it's hard to fuck up in Dominion with these champs imo whereas the other ones can be fucked up more easily.