Deathwatch was the Death of me

Heya, just asking for a few tips. I brought a well-rounded list vs. Deathwatch and I didn't know what to do. Granted, I played Hypercrypt Legion (because I think Starshatter would've been too easy) but boy, was my ass handed to me.

In went second, parked my Monolith and my Doomsday Arc on two objectives in NML and two units just decimated those two in round 2 with no ease, after that I didn't really stand a chance.

I always want to build big units with Necrons, since it synergizes with the Reanimation. However, Space Marines' Oath of Moment (and Deathwatch's two of those in one round) easily decimates said big units.

What do I do? Build many, small units without leaders? I screened as well as I could, but they destroyed too many of my units too quickly. I believe he had 2 x 10 Indomitor Kill Teams and then dome more units.