It will use the setup very similar to DT pChrono with the exception of accuracy sigils, so berserkers and mix of assassins to crit cap. The ratio of assassins/berserkers in fractals will depend on the amount of agony you're going to have. There's also a high chance the dagger/sword + greatsword setup will become very popular.
As for marauders, I wouldn't really recommend it for mesmer in general, because it barely affects your over survivability, and you're not as squishy as zerker ele, for example, so most attacks won't straight up 1shot you.
Any regular t4 group will have a support that will heal you and most likely provide stability and aegis, so extra vitality will just be a wasted stat. And if supports won't, or if you just facetank everything, or your group is bad, you will die anyway. And more advanced groups will cc and phase bosses quickly enough for you to not get hit to death.
But it's not like the world's gonna end if you play with marauder's if you feel like that's your thing, most regular t4 enjoyers probably won't even notice it granted you are able to pull off your rotation and mechanics.