I believe you should be able to achieve this by using as conditions the result measure of a Visit based Business Transaction:
You will need 2 filters:
Visit - User Experience with frustrated user experience and exceeds or equal 1 (as shown below):
and a copy of your visit tag measure with additional check for example Transformation Regex to look for your prime users with again a threshold of exceeds or equal 1 (as shown below):
Your filter depends on the type of the measure, you may also think about the metric performance. If you can replace regex with simple contains/equals/start rule (if for example all your primeUser tag has a unique start or end of the name) this would be the preferred solution.
You would then use your result measure (Visit count with added upper severe threshold to 1) as condition in your incident (to achieve instant results, set evaluation timeframe to 10s).
You would then be alerted when 1 of your prime users has had a frustrated visit. You can then lookup the visits for that timeframe to view the details on what has caused this (as a drilldown from your Business transaction for example).
Hope this helps
So you need both.
Step 1 would be to setup a BT that would use as filter the measure to filter on the frustrated user experience (first screenshot in the previous comment) and as a second filter measure you will need the to create a copy of your visit tag measure when you add additional filter on the prime users (something similar to the second screenshot).
The step 2 is to create an incident rule with the result measure visit count of the previously setup BT. You will need to add a threshold that would trigger the incident rule.
Hope it is clearer now?