I remember the difficulty fluctuated quite a bit, but most importantly that most learning occurs towards the end with VR. I'm not sure what exactly is behind this phenomenon but many people start improving in VR only shortly before the MCAT. It might be because there are less formulas and techniques to master, it's more a way of analyzing and thinking. Just keep on pushing hard and you will eventually improve.
If you really want to know where you are at, take Full-length AAMC tests and see how you are doing on average (with say 3-4 tests).
Still though, EK is great practice, although I too like TPR better for verbal (although not their strategies).