A support summoner, Sunderved is essential for the Mountain Vargath to function, as the units are tough but lack the strength to be able to pressure the opponent unless they are supported by him. Adding +3 Strength in total per turn (+1 per attack) is very powerful and is the core of Mountain Vargath strength in combination with their high life units.
Unlike other factions, the Mountain Vargath do not have a Plan B. If Sunderved is forced out of the picture, it’s a downward spiral from there for the faction. However, because his support ability has a range of 2 and works through gates, it is possible for Sunderved to support the team safely most of the game, even when he is low on life.
If he is under potential pressure, his Epic Event Stronghold can allow him to easily retreat to a safe position.
It's important for most of the game to minimize the chances for the opponent to damage Sunderved, he has 4 strength and especially with Battle Leader may be tempting to use, but you should only do so if it’s reliably safe, often with the afore-mentioned Stronghold as a fallback.