Did we not just get a Heim nerf in 4.5? I coulda swore it was in there. Oh look, here it is. Enjoy. http://na.leagueoflegends.com/en/news/game-updates/patch/patch-45-notes#patch-heimerdinger2
All jokes aside, I think Heim could still use some ballancing due to his safer laning phase than most champs into a weaker late game. The problem tends to lie with the fact that most people don't know how to deal with Heim's turrets (it's easier than you think, harder than you'd hope for) and often give doubles during ganks on him. S
eriously, just take out the turrets. Use abilities to take them out if you have to, stop letting them ff the minions. Bring a flask for more mana, don't pick a melee into him. Just don't feed him, farm under tower till your jungler actually ganks him from behind, then take out the mega turret first because that's all of his damage. After that you can almost dive him to your hearts content.
Liquid Nitrogen is dangerous because it can freeze anything in seconds, which begs the question... Will it blend?
Heimer is typically in the middle or on top, if you honestly can't handle him on top lane swap with your mage ally and enjoy as they use their AOE to kill the turrets and then they burst Heimer to death.
I have never had problems keeping Heimers only strong suit(his turrets) out of commission
Xbox 360 GamerTag: HolyKnight22 PSN: CrimsonDivide Jpn PSN: CrimsonDeath24