My Wizard uses Chill Strike on TAB, and I usually follow it up with Fireball as shooting them back to back seems to speed up the casting time.
From it's first appearance, (for which I and many other are truly grateful...) the explosion VFX has been a bit hit and miss, and often you would not see the heart burst of flames for which the spell is famous.
In the past week or so I've noticed it now hardly ever fires. If I creep up on an enemy and use Fireball as the lead in, then it is probably at about 60%. But in combat, as part of the Chill Strike/FB combo, it's below 25%
One of the reasons we campaigned so hard during Beta was because we (NWO Wizards who spent any time playing D&D in our youth) do love our Fireballs...
Can someone take a look at why this spell in particular seems so reluctant to play its VFX.