I was pretty similar to you. Had pretty significant deviated septum, but no sinus or allergy problems. I had the work done in my first year of riding. I thought it was probably affecting me as well in cycling, and decided to go through with it. It's a pretty significant downtime in your training after the surgery. First of all the surgery blows, and the week after you are totally worthless and miserable. The second week isn't much better, but you at least get the huge crap out of your nose. I had to stay off the bike for two weeks because the intensity could possibly open the wounds back up and start bleeding, and/or remove the stitches. After that, I had sinus blockage for about 3 months, before I truly started to clear up a bit and start breathing like normal.
I can breathe better now though. I have pretty much full usage of both my nostrils. But, I've had a bit more sinus and allergy problems since then. I have to think it is related to having more airflow now. The inside of my nose seems to be dry a lot as well, which again I would assume is from the improved airflow. I haven't noticed a performance or comfort distance while cycling. I breathe out of my nose just as little as I did before.
Is the surgery worth it? I don't know. The surgery was awful, and the full recovery took about 6 months. If I would have known the little of benefits I've had, I'm not sure I would have gone through with it. It's hard to remember before hand though. If I went back, I probably would think I'm suffocating, after having the use of both nostrils for so long, haha.