I don't think it's that mismatched, since people always seem to think Wolverine vs Hulk is a fair fight. It is interesting that Diana used her speed of Mercury in this fight, since writers always tend to nerf her and Superman in the comics and ignore this. Superman gave Batman enough time to fumble around with a second Kryptonite bullet in BvS when logically he should have used his super speed and quickly ended it, I mean wasn't he all worried about his mom (Margo? Marla?) being killed in a certain time limit or something.
Not terrible, but using hot lava was kind of a cop out. It should come down to their individual powers and skills, not "well Flatman totally tricked Cyclops into walking into a poison gas room! Killing him instantly! Ergo Flatman is superior to Cyclops!"