Been playing a lot of Dominion, and AP's are extremely weak.
Around level 12, assassin-types have the following:
1. Extremely fast move speed.
2. Insane burst damage.
3. Short cooldowns.
AP's simply can't keep up with the insanely fast pace and burst damage.
The dominant strategy at this stage of the game seems to be play either an assassin or an assassin counter.
It's really bad.
ADs get a bloodrazor, they an AoE lightning bolt, and their starting item has lifesteal.
Casters need a starting item with spell vamp - NOT mp5.
Casters need larger health pools, cheap cooldown reduction, + movement speed, and more spell vamp from dominion-specific items.
The Role of Casters = Whiff
Casters are typically designed with AoE CC that's effective in large teamfights.
Dominion isn't about large teamfights as much as it is about small-scale 2v2/3v3 type stuff.
I believe this is why AP's are so ineffective in Dominion.
The only AP-based champs I bring are assassins like Ahri and Akali.
I avoid playing Anivia/Malzahar/Brand/Lux, etc.
Ryze would be the exception because he can stack armor/mana, and isn't dependent on slow-moving skillshots.