Is tainted rusher encounters one per planet I only got one in mhenga and tarkus right after i got the probe, roamed for days couldn't get more or is it because I am playing the kineticist class.
Yes, she can be encountered at least once per probe-related planet (except for Zheng Shi Station). If you have already collected the probe for that planet, then she will move on to the next planet, if available--though she will not move on until she has been encountered at least once on the current planet. The character class should not factor into her encounter rate.
So in your case, you have probably found all the prerequisite planets before meeting her, so you'll only see her just once on the planets you already found the probes at. Currently, since there is nowhere else to go, she can be repeatedly encountered on Dhaal.
Hope this helps.