You want an easy team that gets trophies and subsequently will get you easy DNA? On the side make a team of explosives. They don't lose trophies when they die like other units, if they hit their mark they can damage or kill the whole team, it becomes very easy to get Harbingers as you keep playing. I didn't play infected for a long time, when I did I had a difficult time getting DNA and keeping interest. I made a team with only harbingers and killatons; at first mostly harbingers since epics drop less frequently. If you ask your guild for an explosive, same rule, when they die they don't lose trophies either. So if you can beat the map with a minute or more remaining, you get a perfect score. Perfect score equals both allotments of DNA.
I've also found this works with harder maps as you increase your unit level. If you can also research Flare and Geizer that would help too. If you add a harbinger and then flare he becomes invincible for short period, runs right in to the humans, then explodes when the flare expires. Easy DNA from my experience.