It be time to stop thinking about our work in terms of closure. Most everything we rely on is moving away from that and towards positional certainty (error theory based statistics). NGS, standards, etc...
If you have calculated the error ellipse on your closing point, I think that you'll probably find yourself inside that (assuming you keep all your equipment calibrated, in good working order, and without blunders). Not knowing the survey specifics, but assuming you took post processed GPS coordinates as your start and backsight, then traversed to another GPS coordinate, you might propagate the error in angles and distances and come up with an ellipse that matches your result. Your closure in inverse could be anywhere in that ellipse and you'd be surveying to the limits of your equipment and techniques. If you closed flat, that's a matter of chance, it doesn't mean your points on the way there are perfect ... your end value could just as well be any other value in that ellipse ... that's the uncertainty and probability.
Because of GPS's ability to measure accurately over larger distances than our conventional equipment, we have a tendency to consider the coordinates as accurate at all times. That's quickly a problem if we set up an instrument between inter-visible points and take an EDM reading. My own EDM has a standard deviation of 0.006' Considering that with day-to-day dual-occupation, static network, post-processed GPS work we can rarely get better than a 95% confidence ellipse better than 0.03 on GPS'd points we'll typically get an "error" when checking our "good" GPS control.
Earlier in my career I followed a similar methodology to what you describe: GPS main control points and fill in the gaps with conventional traverse. When elevation was a critical factor, there were levels run. In the end, I was left with three sets of disparate data and the difficult task of manually making it all fit together with sufficient confidence for my project's needs.
One day I finally took advice I'd been given for years and looked into least squares adjustment software. Now nearly every project in my shop is run through an LSA program. It has made me a better surveyor many times over by giving me not only a better understanding of measurement error theory and practice, but by showing me consistently and visually how it can be applied to everything we do. I swear just a couple weekends ago when I was processing some baseline work on a deformation monitoring project for a retaining wall I was literally giddy with the way I could see things that unfortunately most people never think of.
It is interesting to find as I show people the software and help them learn (whether my own employees or associates) the younger generation like me has the most difficult time understanding and truly appreciating what it does. An obviously experienced surveyor as yourself would find it a true delight and you'd never want to apply a compass adjustment again!
The key to your project is having sufficient redundant information to make proper assessments of the results and achieve valid accuracy statements.
I have settled on Starnet by StarPlus. While i've become a diehard user, I don't think that any one software is the best solution for each situation. I know that Carlson, for example, has Survnet built in to their survey module and there are surely many programs that others here can suggest as appropriate for your setup. I saw an ad last week for Move3, but I haven't reviewed it yet.
The key in my opinion is to be able to quickly bring all the data together for a simultaneous adjustment. Preferably you're able to bring in the raw GPS vectors, raw angles and distances, etc. If you can't bring the GPS in as raw vectors, then you need to enter those coordinates with true and accurate positional uncertainty. I don't know how you're generating the GPS coordinates, but the program used should be be able to provide this information for each point generated (adjustments in GPS data are by nature LSA). If you're starting off with something weak on GPS like a one-shot RTK position, I'd be careful to hang your traverse data just on that.
It may be out of place, but I have to suggest that ALL traverse for control be a minimum of 2 full sets of angles to tribrach mounted glass (all equipment weekly/monthly checked). There should be a sufficient number of redundant information collected at all opportunities to help you feel comfortable. Things like angles to a natural from multiple positions are great for strengthening a traverse and increasing accuracy.
Enough for now ... I could go on and on, but I don't want to get away from what your specific issues are. Post more detail on your process and I'm sure folks will have some input.