Is there an AI which can "solve" the Path of Exile 1/2 passive skill tree yet?

Solve for what?

The degree of choice point-to-point in the skill tree is actually quite limited in most circumstances. There are obviously items, like thread of hope, intuitive leap, or inversion of choice items like unnatural instinct which change it slightly.

If the question is path optimization to utilizing these nodes, Path of Building already does a good job. If the question is "what single node will give me the most theoretical power." It also solves that.

That's actually the beauty of Path of Exile as a whole - the different systems works in combination to lead to an outcome. As an example, If you're a life stacking build, finding unique ways to get as many life/strength nodes as possible. That's your gear and your passive tree working in tandem.

Speaking about using AI to optimize characters - not just the skill tree - you'd need to build some pretty sophisticated tools which do not yet exist to make that happen. No AI alone would be able to do it.