I am also facing the same issue. The data page rule allows to create test cases for itself but while creating Test suites, the option to choose "Data Page" under rule type is not available whcih is wierd. Further more it appears that Test suites only allows to add test cases which are instance of RULE-AUTOTEST-CASE class but Data Page test cases are of instance of RULE-TEST-UNIT-CASE class. I can imagine that this could be due to ongoing feature enahcenment of exsiting Unit test case framework.
Is there any other rule type already added in Pega v7.2 to create test suites for Data Pages or a patch fix to this issue is yet to come?