Team battle is good event and I love every bit of it.
I will not talk about balance changes here, because it is pretty obvious it will take time to balance all the skills in the game by separating pvp and pve interaction of skills.
Option to turn off enemy or ally costume. Some games do have this option to improve performance and to know what class are you exactly facing. Best example is Guild Wars 2. It takes quite awhile to know in team battle what you are facing because of how distracting costumes are.
Some skills in team battle are very hard to distinguish when its being casted, especially on the wizard class. Sleep, Meteor, etc . This is because there are a lot of instances that you just ask yourself how did you die or how did you get hit. Memorizing the enemy skills and its cd is out of the question.
Let the enemy know where you are casting it, so there will be a chance to avoid it. A good example of skills that are very obvious is Siege burst of Cannoner there is an indication where the skill will hit on the ground. This is a good way to reward players of being aware of skills being casted in an area.
