I would highly doubt that an alliance with only three offensive bots and no ramps will win a regional. From what I saw at BAE, ramps are EVERYTHING in the elimination rounds. I would be comfortable in an alliance of three strong defensive bots with one of them being a strong ramp bot. Sure it would be an ugly way of winning, but three bots playing defense can shut down an opponent (have a look at
qf4m3 at BAE...).
I now believe that a strong alliance would be three bots with very good drive systems who can all play D, sure there has to be some offensive capabilities, but defense can be huge when you have a reliable ramp bot to back you up.