From what I gathered from the forum comments and from various people, the main reason that in PvE cast time abilities are not preferred is because it hurts DPS,
In PvE if cast time abilities would fire off instantly but have a longer cooldown instead that might work better?
In PvP however the cast time allows your enemy to interrupt you, so there it makes sense... What do you think would the instant cast+longer cooldown work there as well, or do you have a good idea to allow these abilities to be interrupted but somehow still make the combat feel faster?