There seems to be no rhyme or reason to which effects show icons in the UI. I just picked up Rend, and unless I’ve just been really unlucky with my 68% chance to proc, I haven’t seen any icon. Not sure there are visual effects either, but then again I have a lot of effects going.
Rend’s visual effect is a little strange symbol (looks like an orange E on its side, kind of? Hard to describe) that hovers over an affected mob’s head. At least, that’s what I’ve been seeing since I got Rend.
EDIT: Here. Where the red arrows are pointing.

Ah, thank you. Rend is not the only one to use that icon, which might be why I was confused. I think it’s for certain bleed effects. Edit: it would be great if there was a page showing all icons of effects. I’m a long time player but I don’t automatically know which is which. Right now I’ve got the Rend icon, a vertical pink sword (lol, don’t even), crossed blue swords and a blue skull.
What else uses it?
I could be wrong, but I think I’ve seen it on my bleed Conjurer. So it would be either Curse of Frailty, Bloody Pox, or Grasping Vines (with all modifier skills).
None of those use that icon.
Not gonna argue with a master like Nine. Do any other skills use it, that you know of?