So a tank and 3 DPS keeping themselves alive? Or a healer and 3 DPS with one of the DPS tanking?
I don't really see this working out for Light Party content, which is likely going to be the majority of "problematic" queues given that there's going to be two shiny new DPS classes to level through the SB story before people get to the Full Party content.

For Full Parties this might work but then I already see PF groups taking an additional DPS for content that can be healed or tanked solo so the only thing this would really effect is DF matchmaking.

Unless we see our parties getting expanded I think it highly unlikely they'd change the matchmaking.