Stacking DOTs

Do Conjure phantasm, Life siphon, and Life transfer[E] stack? Can I get all 3 running on a target at the same time or is there some limit to how many down pips someone can have at one time? Or perhaps only 1 dot working at one time?

I ask this because it seems when I cast Life Siphon on someone and then add Conjure Phantasm it seems like they lose health at the same rate as Phantasm alone.

It never occured to me in the beta that there might be a restriction but now it's going to be a while before I get Life transfer to have something dramatic to test this with.

I only have my Life siphon to 2 pip drains atm so I'm trying to see the difference between 5 and 7 pips which should be noticable I would think but doesn't seem to be...

All degen and regen (health and energy) is capped at 10 pips.