I'm not sure about "as intended", a third of a second of delay is still a bit much, IMHO. .2s should be the upper limit, but it certainly isn't as bad as the UI bugs make it appear to be.
well, it's just that the part of the animation that coincides with the effect happens after the casting bar has filled, giving the impression that the effect is delayed. for some reason, it doesn't happen when you spam the ability. the same thing happens with charged burst and underworld medicine but it's not a hindrance as the animation doesn't prevent you from using other abilities. i find it really hard to believe that this is what's causing all the uproar on the forum.