I can see both sides of the argument here. For one, having Ash's final Pokemon take down the gym leader at its final breath has been a cliche ever since the Falkner battle (Kanto battles were either 1 vs. 1, losses, or pity badges), so the writers deserve some credit for mixing things up a bit. Additionally, as Ash gets stronger, having each gym leader get progressively stronger also seems unrealistic if you aren't using game logic. On the other hand, much of the excitement from gym battles comes from the back-and-forth nature of them. What made Veilstone so exciting was how each side seemed to have an edge at times, where the match was always reeling, but remained close at all times.
Of course, this is simply a general analysis. Once I watch the episode later, I'll be back to rip the stuffing out of it like an enraged comic book guy who had just finished watching an odd-numbered Star Trek movie.
