R2 can only hack into the fire trap network from the base of the Huttball holder. Which gives him unlimited access to all the traps.
Okay the Seperatists are in serious trouble then...
All things considered, the Rebels probably have this in the bag. I've noticed Galen seems to get stronger when he is protecting others, so threatening allies with Galen on the field is the absolute worst tactic you can try.
As far as Luke Skywalker of RotJ, Luke wasn't out to kill Vader, he was trying to avoid it. If Vader had just been some random Sith, Luke would have just taken him down and try to save him if the guy survived the fight... Btw, Luke was probably taught some Ataru (it was Yoda's specialty after all) and definately would have learned Shii-cho (the youngling style). If Luke learned Djem So, he'd also know Shien (which was an offshoot of sorseu).
Add the devious nature of R2-D2 to all of this, and he'd probably be activating and deactivating traps to deliberately catch seperatists in them, I can just see Grievous being char-broiled by R2-D2.
Galen utilized Juyo primarily which is an aggressive style but he also knew shien along with other saber forms. Luke used Djem So, which is the worst form for Dooku to go against if the wielder is very skilled.
Luke vs. Dooku seriously favors Skywalker in the extreme, plus the fact Luke doesn't behave in an obnoxious manner means Dooku is more apt to try enter into his one-on-one duels and would not take kindly to Ventress's interference.
Galen is more apt to use the force to throw people into fire pits, I can see him doing that to Durge and Grievous fairly quickly, and in all honesty I don't think Grievous would impress Galen all that much.