I do not know how is it at higher levels of the game but as low as I am AP Malphite is an issue. Not only for enemy team but also for his own team. His damage is high and teammates that were expecting him to go tank now lack tank in the team composition.
**DISCLAIMER: I AM NOT A BALANCING EXPERT AND NUMBER ARE JUST A WAY TO EXPLAIN MY POINT. THIS IS NOT FINAL. I AM ONLY AN INDIVIDUAL WITH NO REAL BALANCING EXPERIENCE.**
But there is a kind of easy solution. Instead of scaling his abilities with AP you could make them scale less with Armor and MR.
[30/40/50/60/70]+(0.5 * Armor)+(0.5 * MR) => Level 5 200armor and 200MR this ability deals = 270 (true damage) - that's right. The numbers are going to go down and so he will need true damage to balance it out.
[20/27/35/42/50] + (0.2 * armor) + (0.2 * MR) => same situation = 130 (AD).
[30/37/44/51/60] + (0.3 * armor) + (0.3 * MR) => do I need to write those again? = 180 (AD)
[150/200/250] + ( 0.75 * armor ) + ( 0.75 * MR ) => Ok fine... lvl 3 200/200 = 250+150+150 = 550 (AD).
Now you have a nicely balanced hero that is what he is supposed to be (a tank) while also dealing nice damage but cannot one-shot.
So if you see some downsides of this let me know. I will surely read them. I hope riot sees this because it would really help the game's health.
edit #1: Add disclaimer
_**Welcome to Champions & Gameplay!**_
Here you’ll find all sorts of discussions related to playing League of Legends. From discussions about your personal strategies, to speculation about the next champion or patch, if it’s about playing the game, it goes here. If you want to share your love of Lollipoppy, you can write your sonnets and novellas here as well.
Follow the **[Universal Rules](http://boards.euw.leagueoflegends.com/en/c/announcements-en/3eWpXbJi)** and keep content focused on appropriate topics for these Boards.
Use the report button for any post you think deserves the attention of our moderators.