You could. You’d be dismounted just like casting from a flier - except you wouldn’t fall down to splat. Mid-air casting was awesome.
There was hardly anything you had to chase to cast at in Vashj’ir. Casters had zero issues underwater. It was the melee classes and when you needed to face the fishdude or fish with too many teefs around you, that was tougher to orient.
I managed just fine. Maybe you guys just need more PvP combat training - be able to spin to get correct facing.
I liked it… but to be fair… I was a druid so with aquatic form, I basically had axis to flying even when in combat.
So true, the swim speed buff stacked with our natural aquatic form swim speed for insane speed. However everyone got access to a seahorse mount in Vash’jir anyway from questing… allowing mount speed there.
That being said, I like underwater levels - I’m weird for liking the original water temple from OOT (and Majora’s mask) for example.
For sure, but it wasn’t instant cast and it couldn’t be used in combat. 
I loved those too. The only issue I find with WoW water levels is when it comes to combat. It’s really hard to work out depth perception when we’re working with a fixed single view point.
I raid, so I’m used to the awareness aspect of where you are. But mostly it’s not too much of a problem with combat. You just have to get used to the fact that you’re on a multi level platform. You can practice off the coastlines with fish in BFA for example. Not really much different as we’ve had water creatures and some world monsters (see legion) to fight in the water as well.
This post just reminded me how much I hate water temples in the Legend of Zelda games.
Ya, it’s not so much an issue when working with 2 axes to figure out where you are in relation to the mob. Once the third axis is added, without two viewpoints depth perception goes out the window. This is true in the real world if you close one of your eyes. Depth perception is then completely dependent upon an objects appearance relative to adjacent objects as well as your own knowledge of the approximate size of known objects. In game, a lot of that information is not readily available, particularly when you’re out in completely open water. Once a mob finally makes it to you, you can use your own character as a frame of reference. Until then though it can be quite challenging to figure it out with some backing up and some moving forward.
When we’re on land, we can use the ground itself as a point of reference as to where the mob is in relation to our character.
At least that’s my perspective on it.
Edit: A fun RL test of this is to close one of your eyes. Then extend your left hand in front of you and point upwards with your index finger. Next take your right hand and point straight down with your index finger, slowly extend your right hand above your left. When you think your fingers are lined up, go straight down with your right and see if you can match up your fingers. Lots of people are slightly off doing this. Once you’ve tried that, perform the same test with both eyes open and see how much easier it is to know if your fingers are aligned.
I’ve seen things that would scare you shellless!
It was the melee classes
Oh god I guess that’s why I never understood all the hate…melee classes bore me to death anyway, I prefer to fight enemies from a distance…it’s just so much safer.