Scythed Chariots are a joke. Although...
https://www.youtube.com/watch?v=9G2RfJHg9LE
I always have Onagers, unless I need to move quickly. I also use the flames. As few hits as they get, one flame hit takes out as many men as I normally kill anyway using no flame. Though I have learned to put my Onagers either close enough behind my men so an errant flame shot does not take out my own guys, or I put them in front of my men and pull the Onager's operators behind my battle line when the enemy gets close.
I have not tried Pontus much. Their starting infantry and position is always a deterrent for me. I guess first move is to secure Turkey. If you can take Tarsus quickly that will become a bulwark against Egypt. From Turkey take Greece, I guess. I probably will eventually try it. As finances improve it would be important to take Egypt out as well.