NB  is always around 30% CPU usage or above

Created attachment 139464 [details]
IDE log

Created attachment 139465 [details]
<no description>

Tons of sampler threads running all of them trying to dumpAllThreads.

I think this is confusion of cause and effect - the total time of these threads is 89 s and they don't run in parallel but consecutively as a reaction to blocked EDT - it can be easily seen if you invoke select intervals on org.netbeans.modules.sampler.Sampler$1.run

The real resource hog and cause seems to be the editor parsing loop doing the scanning - which somehow slows the whole computer down thus causing the sampling.
I have looked only on some of the beginnings of high activity and it seems that in many cases the scenario is : some editor stuff (highlights, braces matching) leads to parsing which slows down the computer and consequently basic swing stuff takes a lot of time and sampling is started. It may be worth investigating what started the parsing in the first place and whether it is needed...

I doubt that the Editor Parsing Loop is the main cause for all the sampler-awt threads to be started. Its total time is 95s (BTW: compare to the total time of the sampler threads which is 89s) and most of the time is spent waiting for an extremely slow IO. Invoking the 'Select Intervals' action on org.netbeans.modules.sampler.Sampler$1.run as suggested (thanks for the tip), it can be seen that the Editor Parsing Loop had been idle waiting in the time before the first sampler-awt thread was started. The only relevant IDE activity in that time seems to be the 'Refresh-Atfer-WindowActivated' in progress and more than ten RequestProcessor threads running some Maven related tasks. Reassigning to Maven.

the maven related threads I can see are related to jaxws, reassigning for evaluation.

This old bug may not be relevant anymore. If you can still reproduce it in 8.2 development builds please reopen this issue.

Thanks for your cooperation,
NetBeans IDE 8.2 Release Boss