Had a miserable experience. But almost all of the faults are due to issues outside of provider control

If I rate low on performance, it unfairly dings the provider.  
Any tips or suggestions here?

Or maybe just the case to stick to Indy

Sounds like you are saying the actual session with the provider was good for you but some details around getting to the appointment or making the appointment were really bad.

 
In any case, your rating in the review is of the provider, not the agency so looks and her performance are what you would grade. In the general and juicy detail sections you can add information related to both the experience with the provider AND how the agency impacted the over all experience for you.

 
I think if you maybe offer a little better info regarding what was bad others might be able to offer better advice if the above is not of help.

Provider couldn't count the gift. Needed help understanding denominations in currency. I don't hold this against her.

Incall ran out of supplies, no soap for shower, no hand soap for sink. Makes for awkward wash up. Provider embarrassed but in her situation she does not have the means to stock the incall she's assigned. And the incall is a shared resource managed, poorly if that, by said agency.  

Text interruptions during session. This was not clock warnings. Provider even assured that if client is in session, interruptions are unprofessional

Agency schedules clients too close together. Leaving no time for prep, clean, or primp for next. Meanwhile, awkward cleanup with no soap and rushing current client out the door, even as politely as possible

All points to do not repeat, do not go -- but all faults of the agency and not the provider.  Seems unfair to give a poor rating as the provider was doing the best with the conditions that were faced

I'm not sure if this is the best place for my comment, but it is relevant.
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Prior to FOSTA/SESTA, I was able to make appointments with several very good agencies in the northeast. I was almost always flexible about setting a non-clock hour time. That is, I don't need an appointment at 5:00:00.0. If my hostess needs time to relax, prep, etc. and would prefer that I show up at 5:15 or 5:25 or so, I am fine with that.  HOWEVER, I can think of only a handful of occasions when an "odd" start time was allowed.  
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What, if anything, is wrong with scheduling non-00 hours, with reasonable spacing.  
First appt, 9:00-10:00
2nd: 10:20-11:20
3rd: 12:00-13:00  
4th: 13:25-14:25
5th: and so on.
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Your thoughts if any? (copied from escalade1964)