Heim turrets laser charges are still badly implemented
It's nice and over-rewarding to land those skillshots, but the design is just abysmal right now. It takes 91 seconds for a turret to naturally charge it's laser. (1.11% per second) That's worse than Karthus's ultimate at later levels.
Honestly they should revert it, even if they rebalance it from there. It's been enough time to see that it doesn't work as intended. Unless the intention to make him irrelevant.