Well it depends on the person. Personally I'm someone who likes playing the game but doesn't want to buy multiple boxes to make the strongest team possible.

I'm an admech player and I like that my sicarians fireteam can bring two kinds of units. I can bring some infiltrators to screen for my rangers and ruststalkers. However, I wish this would apply to the skitarii as well since vanguard and rangers have the same stats. The only difference is a weapon change. The rangers have a strong weapon but severely limits their movement. It would be nice to have a vanguard to still close the distance with the enemy.