I have a video I can post to prove it, but I don't know how to upload a video to this forum. I was practicing using Khepri's Horn in the current Nightfall on Expert and noticed that ignitions were only doing 8k damage. At Expert, they should be doing around 22k, and they normally do 18k in Grandmasters. I had 2029 power, with the power cap for Expert being 2025.
After further testing by using multiple damage instances, I found that Consecration's ignition damage is 26k (which makes sense due to the bonus ignition damage it gets), and Dragon's Breath's ignitions dealt 22k damage. So, I assume the reduced damage is only for Khepri's Horn.
My guess is that this could be like how ignitions procced below 100 scorch stacks with Heavy Throwing Knife hits do less damage than ignitions activated by 100 scorch stacks. This could be that Khepri's is applying some scorch but not 100 stacks and then triggering an ignition in the same way that the Heavy Throwing Knife does. This is entirely speculation, but that's the only time (other than the previous ignition bug) that I've seen this happen.
Bungie, please fix this. Ignitions are one of the most fun keywords in the game, and they're extremely satisfying, but the ignition bugs are really frustrating.