For those not in the know, Heimerdinger (henceforth referred to as "Heimer" for the sake of my fingers) received a rather sweeping set of changes in Patch 7.10, changes aimed at making one of the worst champions in the game more useful. However, the changes were something of a half-hearted attempt at a fix. Considering the power level of Heimer one would think that sweeping changes would mean sweeping buffs, but Riot Games had a rather different idea. Every buff that Heimer received was accompanied by a nerf that was at least as bad, with the final result being a champion that is probably worse off than when they started.
The greatest irony, however, is that the changes more or less destroyed any hope of mid Heimer once again being viable despite that being Riot's stated goal with the rework in the first place. Why? Because turrets were butchered, and turrets are the only thing that makes Heimer even remotely effective as a mid laner. Consider his other abilities. While his rockets are, in theory, capable of massive damage they are also an extremely hard to hit skill shot that gets blocked by any minions. The only world in which Heimer's rockets are going to serve as effective harass is one where Heimer has already wiped out the minion wave with, say, his turrets. However, the turrets have had half their base damage removed and now take far, far longer to fully charge up their laser blast, which means that Heimer's days of easily clearing waves with his turrets and then harassing the enemy mid laner under their turret with rockets are over. Grenade is all but useless as an offensive tool, so trying to use it to set up a rocket hit is unlikely to be effective, and it's also Heimer's only defensive tool so doing so may also get you killed outright.
Frankly, there's not point to buffing Heimer without either changing his kit entirely. The only way the champion can operate in the mid lane is if he has absolute control of the minion wave, and that's was as true back in Season 1 when Heimer was completely broken as it is now. Riot can buff missiles and grenades all they want, but that isn't going to make Heimer able to compete against the Syndras and Oriannas of the world, both of whom were yet to be released during the days of Heimer's dominance, by the way.
My question for Riot Games is this: What are you afraid of? Ever since his chain nerfs back in Season 1 Heimerdinger has always been a bottom-tier champion, and the only reason he was otherwise back in Season 1 was a mechanic that was eventually removed outright and would never return, Hextech Grenade's damage to champions. Heimer's current design has so many inherent weaknesses that he would need insane buffs to ever be anything more than an annoying counterpick to low-mobility bruisers in the top lane, so these little half-hearted changes aren't going to rock the boat -- at least not outside of ARAM. If you want Heimer to fit into a game that has champions like Syndra, Ahri, and Fizz in it, then it's going to take much, much more than this, and I for one hope that Riot eventually realizes this. As much as I hated playing against Season 1 Heimer -- there's no way to describe how soul-crushing an experience it was to someone who wasn't there -- I would rather see that than endless attempts to "balance" him that ignore the core issue. Heimer is and, unless he's completely changed, will always be all about his turrets. And yet, Riot has done nothing but nerf the turrets for years, to the point where they now have less DPS than Heimer's own auto-attacks.
You want Heimer to be a mid laner again? Then prove it. Until then, stop cluttering up the patch notes with changes that won't do anything but super buff his ARAM win rate. Give him real tools to fight against champions that comically outrange him like Orianna. Give him the tools to combat the huge burst assassins that laugh at his attempts to dance around his turrets. It doesn't bother me that a Syndra pick might as well remove Heimer from the game. It bothers me that he was never there to begin with, since any real mid laner would do the same thing.