Blazing champion actually got nerfed recently because it was too powerful. It would hit you with fire damage EVEN IF YOU WERE IN WATER and was generally a run killer.
They're perfectly fine as is. A situational threat. Keep in mind that water also prevents grass from growing and worsens the power of ice/electric attacks. Blazing champions are also immune to being set on fire which is a big deal as fire damage is one of the most powerful sources of damage. Some combos are also pretty horrifying, like a blazing spider or blazing Scorpio. Shout-out to blazing bats and blazing crabs for doing exactly what you suggested.
They're fine as is now, IMO. You also get to think on how to use them to your advantage by using them to set things on fire.
If I had to buff them, I'd make them able to evaporate the water tile you are standing on with their attack, forcing you to find a new water tile after each attack. Similar to the blazing fist of yog dzewa but not as powerful