Well of course they are going to seem small compared to other steam locomotives. 346 is of course, quite a bit shorter, with smaller wheels, but they seem bigger on this locomotive because overall, 346 is pretty short.
And then you can look at 844, which is around 16 feet tall, with 7 feet of that being wheels. They are huge wheels, but it also has a large boiler.
You cant really see much of the wheels in the K class locmotives because they are outside frame engines, and the wheels are buried behind the rods, counterweights, and the frame, but from memory, I remember seeing the wheels being rather small. compared to the overall locomotive