Is it normal for the pet dragon to be doing most of the damage?

[Kathos]

Depends what you're using, my first time through (for Debir at least, and part of Scarlet) my dragon was going a ton of the damage because I leveled the kick up to something like 540 damage or w/e it is and with inquisitors I just stacked my rage and spammed the kick. Careful though as you can't use the dragon in boss fights so if you put too much effort / runes into training the dragon your army may suffer a bit.
Now though my royal snakes are typically on top, dragon doesn't do much damage because I picked up treasure searcher (impossible mode, need the money badly!) and focus a lot on that. I really only use the dragon for the money, and a bit of combat control with the 1 space knockback (as I don't have slow, unfortunately)