I am not sure I understand what the issue is. For the IR ticket, you need 15 hours of instruction from a CFII to include 1 XC of 250nm with 3 approaches blah blah blah.
So do you have your 15 hours of dual received for your IR ticket?
If you do, there is still nothing wrong with bringing an instructor along with to get some extra input. There could be something that pops up that you may not know how to handle and it would be good to have another head there.
Are you missing out on anything? Well, I say yes - to an extent. If there wasn't something to be learned from solo operations, the FAA would not require 10 hours of it for a private. Some of my most valuable lessons I ever learned are from my student solos and I hope yours were too.
However, remember you are being taught to be single pilot capable. You should be able to handle the flight completely on your own from take off to full approach to minimums, missed and holding completely and totally on your own. That's not to say taking a little extra dual to get you proficient enough to that point is wrong! Just make sure you are not becoming dependent on the guy sitting next to you.
Also, you ARE paying the CFII and not just splitting the cost...right?
Good luck, keep up the good work and before you know it, next raining day when all those VFR pilots are sitting around the FBO waiting for it to clear, you can hop in your airplane and break out on top!
Edit: USMCFLYR you beat me to to it!