Aye they should all flare with appropriate effects (fire for Khorne, ooze/smoke for Nurgle etc.), and if you are wearing an actual Sigil then both your shoulder and orb should flare. A walking Christmas tree.

please no. That glow effect is killing all the sigil, you can not see sigil itleft but that pulse glowing and green clouds if we are talking about MoN.

Since most units can't use the sigils their visuals are just wasted.
So I'm in favor of a change in this regard.

No because I would be super envious.
Our Glowing Halo is a retarded 600 points and I'm only paying for it because it GLOWS.

I REEALLY want to say yes, replace them, so that we all have uber cool visuals on all of our characters...buuuut at the same time it takes away from the feeling of importance and significance when you DO equip a sigil. Long story short I want to say yes but you take away its importance of actually equipping the item. So no, they should stay as they are, more god marks and variants of god marks are on the way they devs had said.