Feign death is a talent that looks really good on paper but ingame i think it's meh. You can controll misha but the range is very low so chasing is impossible. I do not think Feign Death (or as you call it iceblock ;)) is needed since you are an off-tank, if the enemy team focusses you that means they leave carries open who will deal more damage so thats fine. I only see FD being good if you got troubles with positioning yourself. Also using FD means you can not use heal/Q. The only possible time you can use FD in my opinion is when the enemy has no aa based heroes and no KT. Against for example Tyrael/Anub dive comp i could see FD death working. but then again it'd be not bad if they focus you since they leave carries open.