The new format was introduced this season to reduce the number of international windows. However, teams can now play up to four matches during a break lasting from September 24 to October 6.
Speaking ahead of the Netherlands' UEFA Nations League meeting with Serbia on Sunday, Dumfries said he would prefer the previous format.
"I'm not a fan of the current format of the international break, because you're away from the club for quite a long time," Dumfries said.
"So I'd prefer the old format with two matches. But we have to respect the current schedule."
Xavi also believes the workload is becoming a concern, pointing to the number of injuries affecting national teams.
"We need to take care of the players, but the calendar is just really intense," Xavi said.
"There are many injuries across the national teams. It's a difficult period, and maybe it's strange, because it's after the World Cup.
"Four games in a row, travelling; it's too much. Maybe make it periods of three games, or three periods of two games. I think that's much better for the clubs and national teams."
Xavi admitted that changing the international calendar would be difficult but called for clubs and national teams to work together.
"Maybe if everyone pushes together a little bit we'll reach something, but I think next year will be the same as before," he said.
The Netherlands go into the Serbia match second in Group 2 with five points from their opening three games, two behind leaders Greece.
