As a sch, I love when people go after my eos. I can usually get off enough casts between the tank on me to keep eos up + with sustain. Also even if you manage to kill eos, my dps have usually already killed 2 of the people on the enemy team. When I see people trying to kill eos I end up laughing as their dps could be better spent trying to kill me.
I can see it working in a complete 4-pug team vs a 3man premade, or if the sch is just really bad...but I wouldn't really suggest this method to anyone.
edit: I have said eos a lot in this post.