I will preface this with confirming that I am a native speaker of English.
I would say the first two cases given by your co-authors should be corrected though (as many others have pointed out) in the third example the correction is wrong (though I also think it could be written better, and shouldn't have had with).
My feeling is that what you want to do is generate emotion in the reader as they read your paper. You want to build anticipation, tease the solutions and results, and feel the excitement when everything comes together. You want this so that the reader doesn't have to slog through yet another string of logical arguments. One way to achieve this (and I'm guessing this is relevant to at least some cases) is to use less common words from the English language. These may be words that as well as their broad meaning have sublet undertones of meaning flavouring them.
An example of these undertones is my use of flavouring in the previous sentence. Broadly it says there is general information in a sentence, and hints to help understand the meaning of other sentances. Subtlety it suggesting that a writer can take a boring/bland sentence and choose to add further hints of something that makes the text and enjoyment to read.
Another example would be verdant grass, broadly it means "green grass" but carries subtle meanings of lots of life. If we needed to use this in some academic text then maybe we might prefer to avoid verdant if possible. We could then use green grass, but then we've lost the subtle undertones, but perhaps we could fix that by using lush to get lush green grass instead. Now we have something very similar to what we wanted to say but by making use of more common words rather than something that would work brilliantly in a novel.
In addition to my broad thoughts above I'll go through my thoughts on the three sentences and how they could be improved.
For the first example I needed to look up germane, since your primary goal is to communicate information clearly that suggests there would be a better word (e.g. relevant). Only your secondary goal is to make it enjoyable to read, so if making it enjoyable to read requires people to pull out a dictionary or obscure information then it should take a back seat to writing boring but clear text. And don't forget that you should only expect your target audience to be competent at English, not have native level fluency.
these related works are germane to our present discussion.
Why germane? What does this give that related doesn't, is there any difference from what is said by "these works are related to our present discussion". If there is a difference can you correct this simplified sentence using more common words rather then reaching for a less common one.
One reason I could see you might be wanting to do this is to slow the reader down so that they think more about what you just said, and to separate what follows from what you've just written. In which case you could try something else while still restricting yourself to simple words (e.g. use the passive voice), "The work(s) presented in [citation(s)] must be considered for our present discussion" (though I still feel like this sentence could be improved).
...therefore, the scenario considered in [reference] is situated diametrically opposite to ours.
Unlike the first example I (personally) don't have to go to the dictionary for this, though it still feels bad to me. The big picture of what you are saying is
Scenario in [Ref] is not the same as our work.
However there are implications made by your choice of words, something like:
There is a location in parameter space related to our work, and the work in [ref] is located at the complete opposite location.
The parameter space idea probably comes to me because you used "situated" rather than because of "diametrically".
Why not something like "Therefore, the results in [references] are inconsistent with the scenario we've considered." Does this convey the same ideas that you wanted originally, if not could you start from this and generate what you want to say?
The experiments in [references] corroborates with our results
Here corroborates is correct but you shouldn't have with. However I feel like what you are conveying in the subtle undertones is wrong. Broadly you are saying experiments in [refs] agree with our results and thus strengthen our arguement. However at the subtle layer I feel you are saying [refs] decided to check our results and will strengthen our claims which is causally the opposite of what is going on. Depending on what you are trying to say perhaps "Our results corroborate the hypothesis put forward in [ref]". Or if you are trying to use the references to strengthen a claim put forward in your paper, "The experiments in [ref] fit the framework of [put claim here]"
The last thing to remember is that different people will interpret the subtle information differently, though their interpretation is still valid. So when you write like this you can't just assume that everyone will interpret it the same as you do.
But this also means there is flexibility in how you write and so you can develop a style you are comfortable with, enjoy writing, and take pride in the results. However whatever style you develop it must be constrained by the ways that your target audience will interpret it, and the general skill level that the majority of your audience has.