ECM will still be a good defensive upgrade for the DDC, despite of changes about to come. In my opinion you get nice results in current meta if you load up some Long Range Ballistics and PPC's, then apply some nice camo paint to it. I know it sounds oxymoron (It's an Atlas for ****'s sake), but the fact that even averagely good camo + ECM usually gives you a chance to shoot first, provided you've parked in a good position to allow your mech to blend into the background.
(I know you didn't exactly ask for this) Example build:
http://mwo.smurfy-ne...db219b69266ad53
This isn't optimized. It probably is more trouble than what it's worth, but there have been games where I've been able to fire at enemies with impunity for minutes before they returned fire. If nothing else, maybe this can provide some inspiration.
Here's how she looks:

Edit: Oops.. Forgot to adjust CT armor in smurfy (fixed). Should be 120/4. I know having such paper thin back armor has its risks, but more often than not I've been happy having only ~3% of my armor in my rear...
Also you can consider using UAC5 instead of AC 5. In my experience though, AC5 + C.A.S.E. has kept me alive for much longer. Losing RT is especially bad if you have Gauss, since it has a good chance of damaging your CT as it is blown to pieces.
Edited by Kurbutti, 16 May 2013 - 01:04 PM.