For Battlestar Galactica and Serenity (and the other Cortex campaigns I might run), I’ve been using a stripped down “defense” system to speed play.  For players defending against multiple attacks, I have them roll once — either their Agility+Athletic (Dodge) [in hand-to-hand or melee they can use Agility+combat skill to block, parry, etc.] or the Agility straight if they don’t have the skill.  This test, if higher than the base difficulty to hit (say, Average for a bunch of mooks in a karate fight scene) — it’s the skill or attribute check they have to beat; if lower, it’s the 7 for an Average.  To emulate multiple attackers, I giver them a die step on their skill for each mook.

Example:  Martin “th Black Monk” Zhuong is fighting three guys from the Brotherhood of the White Chrysanthemum.  He has a Agility of d10 and a Unarmed combat (Karate) of d10.  The mooks are Agility d6+UC/Karate d6.  The three of them are wailing away at him in a circle and he has to do the Jet Li mutli-block schtick against them  it’s d6+d10 (+2 steps for the extra two guys) vs. Zhuong’s 2d10.  The GM rolls a 6 (they would have missed him even if he didn’t actively defend — most likely, their punches and kicks are getting in each other’s way — and Zhuong rolls a 19.  He easily beats them out, well enough that were this an actual test in a game I would let him have one attack roll at his normal stats, even if he had done multiple rolls.

It works for viper combat in BSG — Skidmark is being harried by three raiders that have her bracketed and locked up.  She is trying to fly them into her wingman’s line of fire, but has to dodge their shots.  Skidmakr is a solid pilot at d8 Agility and d10 Pilot/Viper.  The raiders are combat experienced Cylons with an Agility of d12, and due to experience, a Pilot of d4.  They roll a d12+d8 (for the extra two) vs. Skidmark’s d8+d10…Cylons roll 8, Skidmark 7: one of the raiders tags her viper for 1S+d8 for the cannon damage — a 6 — 1S, 6W.  Skidmark’s Mk VII takes 2W, after the armor.  they’ve stitched her ship, but “it’s nothing she can’t handle…”