It is not my place to comment on your use of language, because I am in a similar situation. I will say a few things that are only partly on topic.
I have been told by some that the quality of academic English, even by native speakers, is often not that great, and that those well versed in literature will sometimes cringe at its verbosity and formulaic phrasing. So the English of a foreigner need not be worse than that of a native speaker, nor should he blindly follow a native speaker's lead.
One reason for this is the fact that there are numerous "schools" in any language: some say the split infinitive is all right, others call it anathema; some consider the past subjunctive dead and buried, others insist upon it; etc. There is probably an "average" group that has certain opinions, and several other, smaller groups that have other opinions. Such a group sometimes condemns what is common practice in another group; this should not be mistaken for what is universally condemned because it sounds foreign, which it is indeed undesirable for anyone.
In my language (Dutch), for example, I believe that some would consider my usage a tiny bit old fashioned and unusual, occasionally. This does not concern me; it is the way I was brought up, it is the way my family speaks and many of my old friends. However, because we are a minority, a foreigner speaking Dutch might be "corrected" by other native speakers if he learnt to speak as I do. Because they do not get my language, they do not get it in a foreigner, and they might say that he was using unusual idioms.
Should this foreigner be concerned? I believe not, though I can imagine that others might disagree. Even so, it is generally not a bad idea to avoid sounding too conspicuous in any way: if you are aware of the fact that a phrase sounds very unusual, it might be a good idea to change it; striving after a balance is never wrong.
I believe that, at least in conservative circles in Northern Europe, the trend has long been to use plain words as much as possible, to avoid using words more complicated or unusual than necessary. I can vouch for those in modern-day Holland and England, and, since this was also the case in the Latin of the age of Cicero, I believe it to be a somewhat universal tendency that may rise in various circumstances at various times. I have also seen signs of this trend in German.
How this tendency manifests itself depends on many things. In English, it means that a writer should be alert when using many words that come from Latin, many proverbs, metaphors, local idioms, passive constructions, novel words, abstract nouns, noun adjectives, etc. This is not to say that he should not use any of those, which is impossible: just that he should not use them too often or in the wrong places. Several branches of this trend have developed in non-conservative circles too, though they are sometimes less rigorous.
So it is best for a foreigner to resist the use of "sophisticated" words for no reason, and use them only when he feels sure that they express his intentions better than simpler words. I do what I can, but resistance is not always easy. Even so, abstaining from any and all idioms and abstractions for fear of doing it wrong will, I believe, generally result in language of lower quality than would taking some risks.
P.S. I am always trying to improve my English, so please feel free to post any tips on my language in the comments. I know I must be making mistakes, and it is hard to correct them if nobody will point them out.