When you know you are going to take heavy losses squad wise, it's best you activate it. If I'm doing a quick base rush or trying to obliterate the enemy out of an area, that's the time I use it. Most of the time an MG + Mortar + Inf will eat your squads up, and if you have Red Tide activated it compensates and replaces them at no cost, which is why it's a very powerful ability.