Battlemaster gear has too low crit values, that is the problem, either u have to spend time to itemize, which is unlogical, or try to reach reach War Hero gear as quickly as possible...
When u reach War Hero, following will happen to a Marauder if u are a MM, u are in cover, so he can't jump and build rage, the u dump him a Diversion canister (u can entrench in the mean if u like ) for the next 10s he will have really difficulties to damage u (his only yellow damage is Force Scream)....now u dump him a Series of Shot 6K damage in 3s, Ambush 5K crit,, followthrough 5K crit, Takedown 5K crit, that is 21K damage inside of 7.5s if he is still alive pop evasion so he will miss another 3s then get out of cover quickly, re-cover, instant snipe then follow through for additional 7K damage, if he can survive 28K damage inside of 12s, then he must have a real good healer.....
Same recipe for Sin Tanks, only they are tanks, it take longer, then it is really usefull to pop shield probe + Orbital Strike on u.....
It's not that simple actually. You are implying that the marauder is someone without access to any of his own CDs. The fight with them is way more subtle. What you listed is pure raw damage that marauder himself can counter pretty well.
Here are a few things fighting any marauder you need to consider:
1. Cloak of pain: if you can find an opportunity not to hurt the marauder for 6 seconds so this thing will run out, take it. Either flash bang (which should be better used for other CDs), or better legshot (which if he is left untouched - 5 sec of him being unable to hurt you. If this is not a 1vs1 fight, forget about it. your team mates will refresh this thing.
2. Saberward: This is very very important to get rid of. You need him to waste it as much as possible, the less time he will have to damage you while its on, the better you will survive. You either need flashbang here, or if you want to waste your shots on damaging him with sabeward on, go for tech damage (at least you will do some damage rather than completely miss). Target acquired can also help, this will be mostly a 130% accuracy vs 50% defense, so you got a 20% miss chance, still better than 50%.
Knocking back: Use your ambush knockback first, followed by a legshot. Cover pulse should be the second knockback. By the time he gets back to you, use ambush again.
Ideally you want cover pulse saved for ravage. You wil always eat 2 hits from ravage, but its important to not allow the third one, which hits as much as the first two combined. 2 hits = 4000 damage, 3 hits = 8000 damage. Why knockback him? well because most often they will ravage you when they are low on rage and their rage building abilities like battering assault are on CD (ravage does not cost rage) , by putting them at distance, not only you interrupt their ravage, but you don't allow them to use their rage building abilities and thus any other stuff like force scream.
Obfuscate: keep an eye for this one. Your MM abilities will not hit anything if you get it on you. And they will aply it because its an ability of global CD. make sure you will notice that debuff icon!! Tech abilities: grenades, corrosive dart, shiv are you friends. You have no idea how many maras have been killed by my shiv simply because i had an access to a 2000 yellow damage ability.
If you are MM, get siege bunker!!!! In combination with ballistic dampers, it will make their super smash a tickling. 400-500 damage smash is nice, isnt't it?
That's about it. It's more difficult to fight 2 marauders at the same time as MM, it not that powerful in this situation. More or less you are supposed to die without help. This is more a case study for engineering, which can handle these situations. I was able to keep civil war nodes from 4 melees for 30 seconds with my engineering, alone.