I don’t subscribe to this view that Schumann was a poor orchestrator. Schumann was a brilliant composer in all departments. A decent set of recordings of his symphonies such as those by Sawallish/ Staatskapelle Dresden are truly admirable. There is no hint of any of the problems you are talking about. There is a good explanation of the apparent balance problems, and it just requires a few tweaks here and there to get the balance right. The result, if done correctly, is well worth it. These 4 symphonies are really excellent. The same is true of much of his chamber works. It goes without saying that his solo piano works are first rate.
In any event I thought that the view you express is somewhat exagerrated and antiquated. More modern opinion is a lot more sympathetic. Indeed there are several sources on the Net to refute this idea of Schumann being a poor orchestrator. It took me only a short time to find the following using a Google search. I'll keep things short but I've seen many others in the past, all saying the same basic thing. Those below should suffice to illustrate the main counter-arguments (the first found at websites for Pomona College, the second at Karttunen.org).
It is fashionable to criticize Robert Schumann for being a "poor orchestrator." Those who offer such an opinion do not usually mean that Schumann was ineffective at finding the right orchestral color to suit the character demanded by the music: indeed, the passion, heroism, and turmoil that are evident in all of his output come across clearly in the orchestral works. Instead, most criticism focuses on his technical knowledge -- for example, whether certain orchestral instruments could or could not play various pitches -- and his handling of balance. The technical knowledge that Schumann somewhat lacked primarily concerned the brass instruments. Until valves became standard on horns and trumpets, those instruments had only limited notes available, a fact which Beethoven, Mozart, and all other earlier composers had to take into account, and a limitation which Schumann had a tendency to disregard or misunderstand. Although Schumann's carelessness in this area is perhaps a trifle embarrassing, it does not indicate any overall lack of talent for writing for the orchestra.
The balance problems that occasionally arise in Schumann's orchestral music are, in most instances, easily solved by making adjustments in the dynamic indications of the various parts. In a few cases, conductors sometimes take it upon themselves to make more serious changes, asking some sections of the orchestra -- most frequently the horns, trumpets, and timpani -- to play notes other than those indicated by the composer. Although purists reject these alterations as arrogant attempts to "improve" on a creative genius, no disrespect is intended: the most venerated symphonies of the great Beethoven are often subjected to exactly the same kind of changes, even (or perhaps especially!) by highly respected conductors, only without the pseudo-justification that Beethoven was a "poor orchestrator."
Another:
Even today one often hears the claim that Schumann's orchestration was in general defective and needs to be improved on. This received idea is so strong that many conductors have never even thought of trying the original scoring. In the end as performances add on to the prejudices of previous generations, the real Schumann becomes more and more difficult to find.
There are in my mind three main reasons for these misunderstandings. Firstly, the orchestra itself has changed a great deal since Schumann's days. The string sections of the orchestras that Schumann wrote for were significantly smaller than today (in Leipzig: 9-8-5-5-4), the music does often sound too thick if played with almost twice the number of string players.
Secondly, the way Schumann's tempo's are treated. Little respect has been paid to the original indications, and the consensus seems to be that either he didn't know what he wanted or the metronome he used was faulty. The problem is that his indications are sometimes uncomfortably fast and sometimes uncomfortably slow. There must be something more than a faulty metronome behind this. There is something in the nature of Schumann's music that make it almost fit within the conventions of a much more straightforward music, but in the end it won't. The irregular phrase structure goes often unnoticed making especially the finales often sound simply repetitive, when in fact there is an subtle play of irregular phrase lengths that, if observed, lightens the music.
Thirdly, the rubato in his music often becomes heavy, especially in the concertos, where one hears a lot of slowing down, but much less going forward. When the tempo fluctuations become too mannered, the irregularities and surprises are hidden and the very nature of the music altered. In the performances of the solo piano pieces one can more often hear the real Schumann, whose music fluctuates between blissful peace and feverish anxiety,
It is surprising how many of us have don't have the curiosity to try out the music the way Schumann wrote it down first and make one's own analyses about the possible problems, however crazy it might sound. Instead, we try to fit Schumann's very unconventional music to conventions that come from nowhere in particular.
Even Schumann's chamber music with piano is said to suffer from bad instrumentation, the piano being written too much in the middle register making balance impossible. Could the different piano of the time have been the reason for this kind of writing? Schumann wrote for what the piano he knew, not the much more powerful instrument of today. If we today feel the music sounds bad on the instruments we use, we could learn from how the music sounded with the instruments he wrote it for and study how something similar can be produced on our instruments.
Many of the mysteries concerning Schumann become clearer if one thinks of his music as being written by a pianist and not a string player. The phrasing and rubato become evident in most cases when one imagines him writing for the piano. Often one hears that Chopin's rubato comes from the Italian opera and to understand Mozart's music one has to listen to his Operas. Schumann's essence is in his piano music.
Topaz