Soulblaze & Surge Staff Lightning Bug

So i notice that when you do Soulblaze with your Ult and or through BB if you hit them with your Surge Staff the Flames get removed. Could it be that you cant have 2 different DoT´s on the same Enemy. I cant say if its only Visualy or like mentioned.

i hope the latter but you cant tell.
Soulblaze is too weak anyway to have Synergy for gaining Warpcharges…