Deep trees of AND/OR are hard to traverse particularly when they are merely the same structure in nested form as a version of the operator that takes an arbitrary number of args.
One potential way to convert the DFS searches into a simpler BFS search is to introduce a new Operator pair named ALL and ANY.
ALL(A, B, C, D, E) represents AND(AND(AND(AND(E, D), C), B), A)
ANY(A, B, C, D, E) represents OR(OR(OR(OR(E, D), C),B),A)
The SemanticAnalyser would be responsible for generating these operators and this would mean that the depth and complexity of traversals for the simplest case of wide AND/OR trees would be trivial.