We get on the phone before we respond to expensive RFPs, and there are questions you can ask (incumbent vendors, past experience with vendors, is there a formal requirement for the RFP, or do they genuinely want real proposals, etc).
On "real" RFPs, especially if you have a good shot, you'll find the purchaser you talk to is accomodating; they'll set aside time for calls to answer questions, and they'll do a good job with your Q&A submission (as a general rule, real RFPs have Q&A phases, though note that you never know whether your Q's are going to other vendors too).
There is an old negotiating trick a bizdev guy taught me once, which is, if you want to figure out whether a deal is real or whether the other side is just wanking, figure out a reason to schedule a meeting on a Saturday. If the deal is big and the other side is serious, they'll do it. Similar idea here, although less aggressive.
If your firm's way of handling the RFP process is to simply pick up the forms off some website, mail them in, and hope, then yes, I can see how the RFP process would upset you.