The higher damage as outline above; out of the 5-10 mages speedcasting in highsteppe anywhere from 0-1 of them are rotation mages because very few put in the time to master a rotation. Being a rotation mage and having done it for 3 years now I have not once injured my arm/wrist/etc from casting.
Slowing down is also not the answer and then there is what you defined as more accurate spellcasting.
What it sounds like is that the more accurate the more damage you do. This is already a thing in the game with the perfect cast, buffing that to encourage slower casting will just do the opposite as suddenly with a perfect cast you get like a 5x damage buff.
There is no good way to deter fireball spam and the people casting at those speeds (the people who are actually at risk) know their limits typically and a few stretch before casting to not only ensure highest damage but also lowest health risk.
Sure little kids could get hurt in vr but that won’t be do to casting fast (I have not met a really young person who casts 2-3 per second) but rather being unaware of their surroundings and play space which is entirely on them with keeping safe in vr and can happen in any game.
Doing anything like making the casting per second limit drop while even keeping the same damage if you upped accuracy damage it will feel like a huge mage nerf and people will quit in droves; people quit when true affliction was nerfed, people quit when triplicity was nerfed, and people will quit when they feel like fireball was nerfed (even if it really was not).
The best solution imo is to teach mage safety with things like stretches. If that does not satisfy the devs could always put a warning label on the class saying that it can cause horrible side effects if not played in moderation.
Also are we sure this is not Pick’s alt just to troll on the forums?