It's really dull on lower difficulties because you can just shoot a ton of arrows and any machine dies easily. Especially when the game first released and the weapons were poorly balanced. However on the harder difficulties the combat is actually impoved, you actually have to hit the weak points of the robot dinosaurs and get them in elemental states, otherwise you'll die instantly. The problem them becomes the game economy, everything just gets really expensive because the harder difficulties are designed around new game+ saves. So the best way to play is probably to use the harder difficulties for gameplay, and lowering the difficulty before buying any gear.