Average rounds per encounter?

[Mustrum_Ridcully]

Are you claiming that all parties have to have a minimum of two strikers? Is that the norm?

If you want shorter combats, DPR or 2 Strikers would be the way to go. But your survivability overall should (ideally) be the same if you have 2 Strikers, a Defender, a Leader and a Controller, or 1 Striker, 2 Defenders, 1 Leader and a Controller. A higher offense means enemies get less time to inflict damage, but a higher defense means you can take (or mitigate) more damage.