Gotta say, I would not alter my adventure/encounter design in the slightest to cope with party design, most specifically "ill-composed parties". To me, being able to cope with and adapt to situations is part of the game. If the party has left a hole in their composition, and they hit an encounter that is difficult as a result, well, let it be difficult.
Let the party understand that the absence of a certain role needs to be accounted for. Feat picks, gear, whatever. The absence of a controller means get some AOE capability, the absence of a leader means get some healing, the absence of a striker means up your damage e.t.c. e.t.c.
A the end of the day, they party made a decision to omit the role. It was their decision, and (to a degree) they must wear the consequences of that decision. We are their DM's, not their nannies.