It's not really the easiest thing to do nor is it the hardest thing to do but it can be time consuming and it's quite unrewarding when you managed to get 2 meltabombs/focus fire on a tank only to have the driver/shooter step out because it doesn't instantly explode after losing all of its health. I personally can't see a reason for tanks to have this I could maybe understand rhinos to give the players a chance to step out but most of the time they just get slaughtered. So you get the kill but you should of gotten it when they decided to stay in the vehicle til its health ran out.
I don't really have an opinion on this since I usually jump out right before the vehicle runs out of health, but I'd just like to point out Does a lone fire dragon often manage to finish off the player in the rhino he just blew up too? I think one way to meet a compromise is to simulate it the way it's done on the TT. Most of the time, your vehicle runs out of health and just becomes a wreck, and its crew are forced out of the vehicle but are otherwise OK. The vehicle only explodes when it suffers from catastrophic damage. So say a vehicle can only explode (and instantly kill everyone inside) when it takes a massive amount of damage as it runs out of health, or when a melta weapon is used against it (since that's what meltas do on the TT) This means the only way you can make a vehicle explode is if you use a melta weapon or a lascannon on it. Not sure about Orks though. Of course, this would probably just make people complain about the fire dragon....
It exists so that Power Fist users do not explode themselves to death when they crack the can open. If it immediately exploded, Power Fist would lose an important part of it's fluff: being an AV weapon as much as AI.
You can use charged attacks to work the healthbar down then use fast attacks or a grenade to push it over. It's why I carried one on my gilded fist loadout.
Like they used too, I would like to point out. When fists were first introduced going after vehicles was a suicide mission. The incapacitated effect was added to prevent this. It also gives vehicle crews a chance to bail out.
That's too much work for melee classes. And thinking. Also I kept blowing up my melee fisting allies, so this is actually an improvement for me as ranged.
Still a problem that wont be addressed because it belongs to marines. I dont see wave after wave of klaw users able to pull off the same thing do you?
I'm not 100% sure how this mechanic works (and tbh, several mechanics are never explained in this game properly), but assuming it doesn't do it already, any vehicle that has been incapacitated should just stop working completely, that includes allowing people to spawn at them (because I'm sure I've seen people do it, and I'm certain I've done it too).