There's an inherent problem with the concept of "OP" in a sandbox game like Minecraft, since there are a lot of different ways and reasons to play it.
I get what your entire point is here, and for the most part I think the loss of the overall forestry interaction system is lamentable, but this notion keeps popping up in various threads and it's bothering the crap out of me. Defining something as OP is eminently possible by any number of heuristics.
1) For a give unit of time-effort value, does a particular mod feature reduce or eliminate that time-effort without either: a) logarithmically expanding resource necessities to generate that feature (true for many forestry features, most RP machines) and/or b) a requisite set of new learned skills (true for RP2 logic gates/FORTH, ComputerCraft sans pastebin).
If you look at matters from this perspective it becomes immediately clear that some mod features are OP, either due to undercosting (XyCraft) or by their very nature (EE). If a mod violates these constraints, the game degenerates toward Creative mode in a certain sense, and you have to begin looking for accomplishment in the artistry of the structures being built. That playstyle has intrinsic merit, to be sure - in the same way art for art's sake has intrinsic merit - but it's worth noting that's it's fundamentally different from the technical/survival roots in which the game is based. You are going from living in a world of digital legos to simply building with them.