The windows are useless. The only way you can make them work is if your enemy
Just happens to be next to it log enough for you to flip the switch. And even then if there is a heart (which would be the point of them going there in the first place), they wouldve healed and moved before taking much damage from sunlight, so yeah.

My advice for a good pvp team, is teammates agree in the king beforehand, and the others focus on protecting him/her, so you can use that opportunity to hit 25 kills faster, unless you're the kind only out to score kills for yourself.