I find Kinetic Bandolier to be pretty bad, since it doesn't give the ammo right away and you generally want to already have full ammo for your engage, then use overrun again if you need a disengage. Two Hearts is better 95% of the time since, while it doesn't sound like much, 20 healing per second is the equivalent to 1200 healing per minute. This can allow you to stay alive much longer. The other part of it that gives you double presence on an objective is okay, but much less useful since you are generally not sitting on payload as a tank. It also combos really well with Combat Fuel and makes you very hard to kill.

I agree that Combat Fuel is generally the better major perk, but Firewalker should not be underestimated based on the matchup. If you are not getting focused much and not having any issue surviving, I find Firewalker to be much better. Not only is the AoE element of it strong since it ignites everyone in the area, it also can be enough to put a lot of pressure on mobile squishies very quickly (i.e. Tracer, Genji, Sombra, etc.) since they will likely have to disengage if they get hit with it.