If you draw the attention of PT, and maras, you will have quite some trouble if you are DF. If you can have a buddy that will keep an eye on you, a tank, a healer or just a sentinel that will draw the attention to himself, then yes DF will pay off. Otherwise, SS or Sab is a safer bet.
I completely disagree with the Marauder comment, PT as a Lethality/DF? Fair enough. Lethality/DF is the squishiest in terms of raw mitigation from talents. Except for ambush/aimedshot knockback you don't lose any of the counter abilties you have and gain a slow off Corrosive/Shrap Bomb. Kiting is just as easy long as you stay within 10m, root them before you reset position, or change targets and roll to distant cover to create a huge gap while not allowing them to leap to you.
Any 'slinger/sniper spec should tear through Marauders when played well, some more difficult than others.
ON THE MAIN TOPIC:
Full sab offers AMAZING utility, CC, and general objective protection with fairly good on demand burst with a proper rotation. It is imo, one of the best point defenders in the capture objective gameplay and is what I recommend if you want to focus on things other than straight out killing.
Hybrid offers more damage.