Which nodes you go for is going to depend on where enemies are and where your teammates are. Going for big nodes first is often a mistake - they will be the nodes that are contested the most. If you capture two B's in the time the other two teams are pointlessly fighting over an A, you've already gained just as many points as them and are in better position to go for future nodes, pinch, etc.

Defending is almost always a bad idea unless you are being pushed. Defending means you aren't going out and seeking kills. Kills feed points to your team, take points away from the enemy team, and give your team BH. Once you take a node, your next step should always be to consult enemy positions on the map and see if there's an opportunity to pinch them.

Points are actually less important than kills. If you look at the breakdown after the game, the winning team virtually always has more points from kills than from objectives.

RNG is an element, but in most cases, the team that wins is the team that played the best. People fixate too much on going after nodes and not enough on making sure they're in a good position. Going after ice on an enemy side of the map puts your guys at risk and also makes you unable to contest ice or nodes or whatever that spawn elsewhere on the map.