But we are in 2018, not 2015. Now there are many more vehicles, and the Vigilante is, by far, the best vehicle for these new Heists (+ Insurgent pick-up). All ACT III preps (less Volatol, of course) is for Vigilante, and there is no danger of dying. Just be smart and know where to shoot.
Going with the Kuruma to kill, from my point of view, seems very "noob" and very slow, when with the Vigilante more very much faster. For example, in Dead Courier, Recovery, with the Vigilante you finish it in 30 seconds to kill everyone and then pick the Savage. Another example is in Barrage prep, with the Vigilantes you stand on a hill and fire all the helicopters, then you use the off-road route to arrive to the airfield and fire again. (Only one player will drive the Barrage)...
1) That sounds like a great way to make a 'noob' error and blow up the helicopter ?
2) is the Vigilante really more explosive resistant in heists than in free roam?
It lacks the 4 seats and handling of the Kuruma and is many times more expensive. Also I'm no fan of the insurgent custom either, especially not for 2 man teams. It offers explosive resistance but isn't really bullet proof at all and it is slow.
The Kuruma is still the best all around heist vehicle IMO it just needs to be used with caution (or not at all) on missions where the enemy fire explosives.