This appears to be a regression from 2.x.
The XML parse operation in DublinCoreXmlFormat.readImpl(InputSource in) appears to take about 4ms to run, of which 2ms is:
and another 2ms for:
This is problematic when a lot of XML catalogs are parsed for the same request, as for (parsing XML catalogs for a large number of series).
It seems this was much faster in 2.x, although it's not clear why.
Possibly strategies to improve this include re-using the SAXParserFactory rather than creating a new one for each call. Some discussion here:
Best is to avoid storing commonly-used attributes only inside XML blobs.