DePaul-Notre Dame was among the top rivalries in the country  during the schools’ days as independents, and it had the promise of rekindling when the Blue Demons joined the Fighting Irish in the Big East in 2005. But Notre Dame and DePaul have gone in different directions in recent years, with the Irish remaining among the better teams in the country and the Demons struggling. That doesn’t make for much of a rivalry, does it? ‘‘It is for us; it really is,’’ Notre Dame coach Mike Brey said. ‘‘When I got this job 13 years ago, the first thing people …