I war, I run mono since a few months and quite happy with it. I have done 1 very bad war, 1 absolutely amazing, and most where OK/good.
For the record, my defense team is at 4100+ TP, and our wars have usually 10 players over 4000TP, the rest between 3300 - 3900.
I don’t have enough depth to align several attack teams over 4000, and my alliance expect me to take down a few of the strongest ennemy teams. So I go with 5 mono teams and the 6th team is built depending on what is left on the field.
I had one war where nothing went normal, mostly bad boards and bad decisions from me. But I also had one war, were my 5 rainbow teams (TP between 3500 and 3700) took down 5 ennemies with TP above 4000.
I will probably move to 3-2 teams when I have enough heroes to make great team combinations.