if it ticks it's a dot, if it's brown/orange numbers it's a single dot, if it's white/yellow (crit) it's aoe, that's how I've looked at it, could be wrong.
As for the cp passives, it's a hard one, because for example poison injection I noticed a benefit from both mighty (increases poison damage) and thurmatage(increases dot effectiveness) through just testing on enemies.
Maybe a tool tip bug? Maybe a cap? Maybe not enough points to warrant a significant boost? No clue on that one.
Could hurricane not benefit from the elemental damage too? Considering enemies fry like the Lightning effect?