Hard to says. At times the skill level has felt all over the place. And I'm lacking a working knowledge of "rank = x aptitude" currently. ^^;
However, and if it fits your playstyle, a hug contribution you can make in any Tower Control match is inking. Ink the ground. Ink the walls. Ink your teammates' feet when they're in trouble. Ink the top and sides of the tower when it's nearby. Ink the enemy team just because. Ink everything with your brush. Ink everything with your autobombs. Ink everything with your inkjet. Ink all the things with all the things!
Having most of the map, especially key parts of it, in your colour grants your team a massive boon while stifiling the other team's progress. And becomes overwhelming when your team gains momentum, even when you're losing. And depending on your random team comp, a sea of ink allows many weapons to reach their potentials. Blasters and rollers are free to hunt, long range users can remain untouched, aggressives can go around picking fights unhindered, etc.
As for the tower, try to avoid getting on it unless necessary, such as 3-4 members of the other team is down, you're in a desperate push, you need to bum a ride to somewhere on the map, etc. And avoid attacking someone on the tower from below it. Either when you're level with the platform or from above.