I was doing general hard mode last night and when i tryed to teleport out of a shadow crash i kept getting the message invalid target. I was wondering if anyone else has gotten this bug or if it just part of the encounter?
It's not a bug, as mentioned you need to start the fight and then place the circle. It's been done so you are forced to spend mana on an ability that helps you during the fight.
I've never encountered this problem, not when placing the summoning circle before entering combat either, but I suggest you try and put it up after entering combat.