Originally Posted by Thth
As I stated, there's no point to build up armour on Heimerdinger as enemies cannot get to him with proper play; especially not when build to nuke.
I think a lot of people fail to realize how many ways there are to "win" this game. The idea that Heimer needs HP belongs to mid level players who think that everything and then some is decided by team fights and ganks.
This is not the case, as Heimer is built around maintaining a siege on an enemy tower. He doesn't need to expose himself while sieging, he just needs to run in, drop a grenade and a turret, and run out. This resuts in minimum exposure, so stacking damage is much more effective to bring towers down quickly. However, this can lead to problems if your team is based around ganking and team fights.
For example, imagine a team with Amumu, Pantheon, Tristana and Fiddlesticks. This team would win by constant ganking and forcing team fights (which it would win due to it's massive amount of AoE). Heimer could certainly help, as he still deals some damage, but there are other champs that would be better: Morgana would deal more AoE damage and have more CC, Ashe could add more overall damage, etcetc.
If, however, the team has Alistar, Soraka, Nidalee and Sivir, Heimer would fit in perfectly. A team with those champs would allow you to maintain a constant siege. HP is a non-issue, because 1) You won't be taking damage anyway and 2) Three healers mean you get back any life you do lose. Sivir is as great of a pusher as Heimer, so working together you can expect instantly dead creep waves and non-stop grenades. Kayle, Alistar and Nidalee are all great pushers in their own regard, too. You could literally maintain a siege line in front of the enemy tower with all five enemies standing guard, and blow the tower to pieces anyway.
The only time Heimer should get focused is when he lets himself be focused, or during team battles. Heimer is not geared towards team battles, he's geared towards pushing. Building HP on Heimer would make him better in team battles, but in that case you should just choose a champion who has the capability to do well in team battles and leave Heimer for those who know how to use him.