One-shot of evil villains

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So a couple of guys in our regular group can`t play this upcoming session, tomorrow. As an alternative to the regular campaign, I am preparing this oneshot where they play evil characters who are tied to a cult that the main characers are fighting these days. So I have maid a few premade characters for the remaining guys to choose from. Six premades, four players.
The thing is that I made the characters based on concepts I had, and inspired by my new Heroes of Shadow and Book of Vile Darkness, I ended up with a nasty crew of cool vilains. However, there`s no defender and a random chance of what roles the characters that the players will pick, are going to have. Not a big problem! I have open form skill challanges where the characters get a chance to take control of the narrative, a heavy focus on roleplaying, and I am adapt at adjusting combat encounter on the fly if they are too hard or too easy or if something unexpected happens. However, I would like some tips of what kind of encounters would be fun and fit every kind of group without a defender, even potensialy three strikers and a controller  or a leader.
The reason that the players can`t pick characters yet, is because I have three opening scenes where I introduse the six characters first. After that, they get to pick.

Here are the premades:

Angel of Death - deva hexblade (striker)
Scarecrow - revenant swarm-druid (controller)
Ivan Mandrakov - vryloka blackguard (striker)
Grigori Mandrakov - vryloka vampire (striker)
Dripping Crow`sclaw - shadar-kai shaman (leader)
Grim Shadowstrider -  Shade Binder (controller)

4 players, 6 characters to choose from, many possible combinations. Any tips?