Stack colors. Check this topic about that if you’re not already familiar with it: Titan Attack Fundamentals - (new player Titan guide)
I can’t recall when I was using healer last time, juggling around 1200-1400 cups. I have strong Sabina, 3.60, but I think she’ll stay like that for some time, and I’ll raise my Sartana further.
I have few approaches - either I do 2 colors strong against tank + 2 tank color + wu (or I put someone else instead of wu if he’s among first 4), or I go 3 strong colors against the tank + 2 strongest heroes to survive longer (usually when tank is rigard, kashrek, or purple/yellow). Once I tried 3+2 colors and it ended great, but second time not so much 
Not everytime is win, and war is especially hard, but I find it more fun and making my brain work than when I try going rainbow. I do try rainbow from time to time, for farming, to see how new hero’s special work or to see how strong they are… like baby training
But for anything serious, I stack colors.