I wouldn't even call TF an AP Carry. He can do a lot of damage but it's more so burst than sustained. His gold card is nice but it's also very windowed comparative to something like old Taric/Sion. In addition, it's based on auto-range. Which is 525. That's not very far. Ryze doesn't have a stun so I'll just skip that.
At this point you're asking "Well why does TF get to keep his stun and Taric/Sion don't?" Simply put:
- 1.) Targeted abilities take up a lot of power budget.
Why do you think wild cards are slow-moving and poor at clearing unless they're in a straight line? Why do you think TF's passive and R have zero damage while his E is 155 (+50% AP) damage at max rank. Ryze has his root but he's busted and shouldn't be an example to follow. (Frankly he shouldn't have his root be a PaC)
- 2.) Sion and Taric stuns were true point-and-clicks, TF isn't.
TF has to cycle through to his gold card as well as land it in the alloted time. Sion/Taric clicked you and stunned you. In Sion's case, instantly. "Oh but messing up your TF ca-" EVEN PROS have messed up the gold card. It's not always as easy as it looks under circumstances.