Saying that Jayce has more HP/level than most tanks is a useless statement.
It means nothing at all, well, it might me that you can't put 2 and 2 together.
Zed has a lower base AD than Shen. This is not an issue because shen does not have AD steroids in his kit. If Zed had AD steroids in his kit then you could very well see a zed running around with 600 AD with no issue.
The same applies to tanks. Jayce has no(i think, too lazy to fact check), tanks steroids in his kit. That means that not only does he not build health, he does not have anything to make his base HP worth more(no shields, AOE dodge circles, massive regen, % damage reduction, stat stick passives).
