A question about Mind Blast

Im levelling a new toon, a priest which is a class I havent played that much recently. She is about level 7 at the moment and one thing Ive noticed that feels odd is how Mind Blast works.

The spell has a 1.5s cast time. So if I target something and hit the key to start casting the spell, the target is actually indicating an effect before I finish casting it. So if they are close they respond before I’ve even finished casting. However, if I use something like Smite, they dont react until the attack actually hits them.

Has this spell always been that way, and is there any reason why it should behave different to any other attack?

If you read the description mind blast “causes high threat” so that could be it

I get that but Id assume it causes threat after it actually hits the target. It just puzzles me that they react to it even more Ive finished casting it.

Might be the act of casting. Same as a renew on someone can bring you threat even though you didn’t touch that add coming at you cause you renewed the tank

Hmm. OK. I guess its no big deal, I just adjust my rotation and dont cast it first. Just seems unintuitive, if you get my point.