Heimerdinger's hp regen took a serious hit with preseason changes.

So, Heimerdinger used to benefit from his passive, but had no innate regen. This wouldn't work with the new regen items, so they removed his benefitting from his own passive (which starts at 10 hp/5) and gave him 10 hp/5.

The problem with this is that Heimer's passive scales to 30 hp/5 as he levels up. So Heimer is now missing up to 20 hp/5 as he levels, which is fairly substantial.

The obvious solution is just to have Heimer benefit from his passive upgrades (i.e. he still has 10 hp/5 base so he can benefit from regen items, but when his passive upgrades he gets additional hp/5. In other words, make him benefit from his passive again, but 10 hp/5 less for him than his allies). This will bring Heimer's hp regen back to prepatch levels.

Please, the Dinger needs you to raise your dongers now more than ever. Give him back his hp/5!