There are several things in your explanation that I do not understand. But what I think I do understand is that you had 4 equal cost links and you were doing load sharing over these links. Performance was not good (at least for some applications) and you stopped doing load sharing (I think perhaps using a single link) and performance improved.
If that understanding is correct then my first question is whether the equal cost links were really equal capacity and equal performance links. The kind of symptoms that you describe are frequently associated with out of order packets. And out of order packets can sometimes be caused by using links that are of unequal capacity or when some links have much higher packet loss than other links.
I offer this suggestion as something that you might consider. You could continue to use a preferred path for most traffic. Then you could configure Policy Based Routing and send traffic for selected applications over one of the other links. In this way each application would be using a single link and have the advantage of a single link but each of your links could be used for certain types of traffic.
HTH
Rick
HTH
Rick