Small amounts of coccidia is nothing to worry about as long as he is gaining wieght and appears healthy, he is fine. I wish I had the choice to just up and leave a seemingly good vet becuase i was upset that he would not give more albon. Just like everything in life too much of anything is always a problem.
I know it has taken me 6 long years to find a vet that was able to treat and diagnose the simplest of ailments. Two dead lizards later and a hour drive and i am finally happy about my choice in reptile vets.
I suggest before moving to a new vets office talk about your concerns with your vet and hear his side of the story, make yourself as knowledgable as possible about coccidia and anything else you are worried about and if he listens to you and validates your concerns stay with him. even if he DOES NOT give more albon!!
i would switch if after you researched on your own, made knowledgeable choices, and were still told you were wrong. IE. my wd had mouth rot .. i knew it, everyone that looked at her knew it but my vet and her colleagues told me no, it was just sores from stress... (DUH)... bad vet get a new one.
and for the record I adopted suzie who had mutliple problems including mouth rot and a URI. Even under strict quarantine she/he was able to get my very healthy male wd sick. He died in dec 2000, she/he lived for three more years and was euthanized in the beginning of feb 04 because of a severe eye infection and a failure to thrive.
JMO...take it or leave it... and btw.. i think that is a good wieght and legnth for a dragon his age 
Alissa