I noticed my KDR was a little poorer after switching to barebones from core, and I chalked it up to not playing for killstreaks. I tend to play a little more recklessly since death isn't as important. That especially holds true for domination, where getting killed a few times while capping isn't feeding an enemy killstreak.
In core, when I have an attack heli up and my next killstreak is a reaper, I tend to play it a little safer until those last couple of kills rack up. It doesn't have to mean camping, but you ADS or go prone around corners, that kind of thing, instead of just running full Leroy at the enemy.
