Probably Yareli, she is quite tanky even in steel path and even if your surfboard dies, its one button press and instantly back up. Combine with ocucor and you just sorta roomba the map. Screw some of the grineer layouts tho.
Boltor is my favorite so far, im using Telos because im a sucker for the effect on low level maps as a map nuke. Projectile weapons have a place in my heart when im able to recreate passion of the christ in bulk on enemies.