Necromancer is likely the class you want to play
it used to have longer dots than now but it still has them
ideally you have 5 dots on your enemy, the 3 main-venoms (Wandering Fever, Neurotoxin, Avaricious Shadow)
the toxin from hellion (2nd ruby grid downside), the bloodplague (red reptilian eye, is an aoe but brings in supportaspect nice debuffs even in ST) + with a longer cd there is also a racial skill which is also a dot (green acid ball icon, dont know the name)
while it is not a dot technically, the continous attacks from the hellion are also like a dot as it autofollows the enemy
you might read here for more info
https://allods.my.com/sites/allods.my.co…ecromancer.html