Just curious.
As a wingman and ghost stomper. 
You stay back near spawn , behind cover surrounded by teammate foot soldiers while waiting to take on enemy as they appear. Ideally , you want to prioritize killing enemy vehicles , but if you are hunting for foot soldiers , choose to either gun him down with the right trigger turret in spurts as to not overheat it. Or lead with your left trigger missle launcher aiming at their feet . But do not do both unless they are close by and in front of you (just a bit out of stomp range). Learn the damage radius of the mech’s stomp well . It mainly works outwards in front of you like an open fan from 10 o’clock to 2 o clock.
Also when expecting an enemy vehicle to round a corner, anticipate it with a fully charged 6 missle load up and release.
There you go.
2.62 kd
It depends on the gametype and map. For example, I always use it defensively in any Capture the Flag gametype. It’s just the most reliable flag defense there is, in my opinion. In King of the Hill, I try to sit at a distance and pepper the hill, to provide support. In Infinity Slayer, I go wherever my heart desires, but I try not to get boarded or destroyed.
The main idea is that the Mantis is a DEFENSIVE vehicle. You go out into the open and you will die in a matter of seconds. Try to stay near your base, near lots of cover, and make sure you have team mates around you to help protect you.
For attacking enemies:
I’ve found it best to always have 5 rockets available. If I have less than 5, I’ll just fire them at the direction of the enemy.
I usually fire my rockets in a salvo of all 5 at once to try and take down an enemy/vehicle. If you somehow haven’t taken them down, then you can use your machine gun.
The main key to keeping yourself alive is to either empty out your rockets or overheat the machine gun but NOT BOTH at the same time. As one is reloading/cooling down, use the other weapon to keep enemies back.
And melee is your best friend for enemies walking up. If an enemy is rushing directly towards you and you initiate a melee attack and get stunned immediately afterwards, your Mantis will be stunned but will still follow through with the melee. They’ll never expect it.
I move up with my team, and I only move with my team. That’s what lets me get pretty decent streaks in a Mantis, if my team moves up, I move up with them, if my team retreats, I move back with them.
I operate pretty much the same way in a Banshee to get sprees, as well. People can’t just look up in the sky and target you, and only you, if they’re actively being engaged by your teammates. If they do look up, your teammates get an easier kill, if they don’t, then you get to save your teammates. Coordination with teammates is what makes vehicles strong, I’ve seen more rampages with vehicles in this game than I have in any other Halo, but the key is that those people who keep their vehicles alive for a long time don’t try to solo the whole enemy team by themselves.
I tend to stay back at spawn, I only push when I know the other team is crap.