Whats your rebound like, are you using all or part of your available adjustment ? If you have plenty of clicks left, then viscosity can’t be far off. If you have used all of you rebound adjustment then a heavier weight oil is needed. You could also increase the lube oil level in the none damping leg, eg. in my Rev’s I have increased lube oil level from 5cc to 20cc. This gives less air volume in that leg, so ramps up pressure when compressed quicker and prevents diving into the travel as much. Also helps lubing the bushes, as more oil is splashing around.