When you make multiple attacks, you split your dice pool, but as far as I can tell you don't split the defense penalty based on rate of fire. e.g. a sam with 18 dice for automatics could fire full-auto and attack three targets (or one target three times) with 6 dice per attack, and each of those targets would have a -9 defense modifier. That's almost as effective as three separate semi-auto attacks.
I had been thinking that the rule of one attack per action phase made firearms less effective against multiple targets than previous editions -- two simple bursts was always more effective than splitting your dice pool -- but changing BF/FA to a defense penalty looks like a significant boost to multiple attacks that balances it out.
If lots of bullets is the most effective option, that also makes the new recoil rules make more sense. Assuming they're meant to be read as "Recoil penalties are cumulative ... unless the character takes ... an action other than (shooting for an entire Action Phase)" (parentheses added) as has been indicated by the designers, that means any non-shooting simple action will reset your recoil. So then it's easy to take a simple action to shoot and a simple action for something else every combat phase and never worry about recoil buildup. If firing full-auto is the most attractive option, though, it means you really have to plan out your recoil.