This is simply something I am testing for myself at the moment to do some theorycrafting for dominion and to eventually perhaps publish my Heimerdinger playstyle.

As for my general style, I am currently working on developing an offtank-DPS heimer that is mostly a HP tank rather than one with a little less HP and more mitigation. From my few games in the beta I saw most competent people picking carries or tanks, and going for straight up DPS or mostly tank items.

Because Heimerdinger is a very stong late game character, and you will want to make your dominion games last as long as possible so that you can get the full benefit out of your long time investment items (Archangel's and Rod of Ages). Obviously winning early is a big pro, but at higher levels, I feel that dominion does not have so much of the positive feedback mechanisms as Classic mode does. This idea came to me after my final beta game, in which we happened to lose from a 180-24 lead that the opponents held while melting us down steadily. Their carries were simply too much for my team to handle, even though I could confidently take any single one of them on at a time.

The general idea for me is to camp a point which is likely to get pushed and set up two turrets as far apart as possible, while making sure that a melee champion attacking one is within the other's field of fire. I then poke as hard as possible, even letting myself take some damage, with the sole intention of getting an enemy to chase me into range of both of my turrets. Once I can being chased and close to my turrets, I save stun grenade to use it point blank when the enemy champion is right between my two turrets.