I think that INS is typically much worse than most government agencies because of its situation, which won't change:

1) Its customers are not voters, so it isn't accountable to them. Your attempt to get constituent services from a congressional staff is probably the best way to make them treat you as a citizen, but even that doesn't happen fast. It would work better if you were a whole company needing workers, and not just a single citizen. Dragan's current employer in Charlottesville called their congressman on his behalf in order to get his H1B visa freed up, which still didn't happen overnight.

2) The INS basically exists for the purpose of keeping people out. Technically, their mandate may be to "manage" immigration as well as to restrict it. But a big part of their job is to say "no" to a lot of people. It will stay that way until the public decides to let everyone in, which it won't.

3) I think that the number of immigrants varies quite a bit from year to year and has been generally rising. I doubt whether the INS consistently gets additional resources when needed.