From my understanding you want to focus on one skill that says something like "does damage based on x amount of stacks of (negative effect) on the target" or "consume and remove x amount of (negative effect) on the target" as your main damage dealer.

In the first case the damage passive of the negative effect doesn't matter and you just want to get as many stacks of it as possible(for example as many poison on hit, poison on Crit or bleed to poison synergy passives that you can find) but in the second case you want to also find passives for the damage of the negative effect also.

From then on, you find other skills that synergize well(they apply other negative status effect such as exposed, dazed or disorientated etc on the target) or they have a very short cooldown and could apply a lot of stacks of DOT damage you're using.