There's a few differences. First, masters become like these glorified diamonds. They are extremely good, but grand masters got what it takes to know everything. Aside from skill, knowledge, and aiming. Grandmasters are more aware. They know their healers are dead, so they check and don't spam. Regular masters spam and are still kinda idiots. There's also, those that solo there playing a variety of characters are true grandmasters. Those that play in groups usings 1-3 characters lack a lot of things but know the meaning of teamwork