http://www.youtube.com/watch?v=hxhmskeCZJs
would something like this work on Dominion if the team already had enough utility, or is malph still better as an utility lighting rod in the crystal scar?

Rather than a lightning rod, Malphite is better considered an auto-attack AD counter because of his hefty AS slow and how well Frozen Heart meshes into his kit.

Armor Penetration is rife in Dominion at the moment so Malphite struggles to get to the point of unkillable, but he can be decently tanky enough.

I would never take a Crit / AD Malphite build though. It's simply too expensive and doesn't do enough damage when compared to all the bruiser champs running around on Dom who deal FAR FAR more damage while still being semi-beefy.

I have no idea how Critphite would be useful when his ult is on CD and the other team kites him

Have you seen any Tryndameres or AD Yis do well on Dominion lately?

Malphite has what is probably the strongest AD steroid in the game.

It's more like that on SR Malphite can afford to jerk it in the jungle or something until his ult comes back up again and your team can usually accomplish something while people are dead from your ult + SOTD. In Dominion you basically have to be ready for fights at any time, which is why ult-oriented characters tend to have difficulties since they're balanced around their game-turning ults.

I've played it a few times, it can work very well or completely fail depending on the team comps. The main problem is it by time you have the items you need the game is about over.