How to improve my team defense?

Hi guys i play in this great game since 6 months. I am level 30 and have some good heroes even if my depth is not big yet. I am starting to do very well offensively and in raids i can get revanche win against mostly 3000, 3100 and some 3200. That said my team defense sucks mostly. I am with 1400 cups and have hard time to do better.

I use team 2 as defense but i change often with mostly the same result except for team 6 which is the team i will use later when the heroes will be better.

What team or what change should i do to do better defensively (i know there will always be someone to lose against)?

Thanks