So I have used Seeker Chariots in enough games now to figure out the real problem with them. It's not that they only have two HP and become relatively useless after even a single glancing hit, or that they are immobilized on a 3+, or that the Alluress always dies when she hits combat, or that the large base makes deep striking them tricky, or that they can't sweep if they win combat, or that they can't be locked in combat to protect them from shooting, although those are all fine points.
No, the real problem with the Seeker Chariots is that it is a total bear to get more than one of them into base contact with the target on the charge when you factor in terrain. Without a dozer blade, those things are a rolling failed terrain check. I would argue that they should ignore difficult terrain or have a dozer blade equivalent standard. Even in open terrain, there often isn't enough space to fit more than one model into BTB contact with the target, so you totally lose out on the hammer of wrath attacks that were the reason you took them in the first place.
I run three basic chariots because they're too easily destroyed to justify spending more than twice the price for two extra HP. Plus that costs a lot of ducats for a strictly fun unit. With three, I usually manage to get at least one charge off, but I'm lucky if two make BTB.
This means that even if the Seeker Chariots are drastically improved in the new book, they'll still be kind of lousy unless they are totally revamped. They're a distraction at best if they stay how they are. I use the Chariots as move blockers, mostly because half the chariot's offense comes from exploding in the enemy's face (which is teh funnie).
This also has me dubious of the upcoming Khorne and Tzeentch chariots. Khorne especially because you know it's going to be built to charge things. The Tzeentch chariot will probably be a fast skimmer that's shooty, so that's fine. My guess is that the Khorne cannon model is going to be the better choice of the two.
I hope all of the chariots are worth taking in the new book because I enjoy playing Seeker Chariots, but I'm extremely skeptical at this point.