First of I'd like to thank you for taking your time to read this post.
We can all agree that Hextech is super powerful even if you only have two of the champions. I'm here to propose some changes to how the mechanic works and how it targets.
I feel like you should make it so that 2 Hextech units disable items on ONE champion for 4 seconds and then if you have all 4 it disables items on ONE champion for 8 seconds. It's possible that you could make it target TWO champions if you have all 4, but then I think the 8 seconds should still be 4 or maybe 6 if you want to find a middleground. I would test this out a lot before changing it to get these numbers right, but right now it feels very unfair to play against mostly because of the weird positioning you have to do that is very bad against everything else. If you spread your carries with items you're weak to assassins and things like Blitzcrank or Vi AND they have trouble hitting things right away because of their range (unless you have Rapidfire).
The way I see it, this was introduced as a counter to item stacking which it has proven very effective at. If you decide to use the fixes I've mentioned you still counter item stacking on a single carry, but you can still play around it by having items spread a bit like having Morelloes and GA on Kennen while also having let's say Ashe stacked with Rapidfire and Rageblade and some other champion like Braum with tank items. This also makes it so that the positioning of the units doesn't get super awkward because it doesn't target the champions around the target, but only that one champion.
If hextech worked like this, it obviously wouldn't be as powerful, but it's such a hard mechanic to balance that I think making it weaker especially if you only have 2 of them is the better option. I also still think it would be strong enough, but this would make it so that splashing 2 into a comp wouldn't be as strong. You would pretty much need to get all 4 to make it powerful which I think is better for the balance. I believe that making it require all 4 is also good because it's supposed to rely on a 4-cost unit (Jinx) and so it should be of equal power to other comps with expensive units.
Once again thanks for reading and I hope you have a great day!
//Lina aka SmukkeHund on the Fields of Justice!