Not trying to be a "Smart Alec" but "In Seconds" To me means anything under 60..AKA a Minute. And it was used as a vague description on purpose to note that I dont know how long it was...But it was very short
If not I would have said a specific number of seconds......
Fair enough, to me it seemed to indicate the lower end of the spectrum in your case as you seemed particularly distressed at how fast you were killed. Any DPS class can destroy another DPS class "in seconds" if you consider that to be up to a minute.
In any case, it's worth a try but I doubt you will do much better with Vengeance. I never found the spec particularly effective versus assassins. You will be marginally more effective than Rage vs assassins as you use less force attacks and are not reliant on an AOE, but with the rather incredible amount of CC they have they will be able to negate most of your ravages and without those Vengeance does not have near equal dps output as Rage.
In the end they still have the upper hand in terms of dps/survivability ratio, and you will be less effective against pretty much every other class except maybe AP Powertechs (30% AOE damage reduction) and maybe Snipers (60% AOE damage reduction but only when entrenched). However Vengeance is much more interesting (and imo more fun) to play