Sion in a bush

So i have recently played a game as olaf against a poppy and sion duo top lane. needless to say i was dived constantly and died often (poppy would ult me when low and tank the turret with it as sion wailed on me with massive cc and shield damage.)But thats not what im complaining about. So you see, after the 2 of them were fed to the gill diving me when i couldnt do anything, and our shaco was to squishy to help, poppy would go and gank for mid/bot and get them kills as well, leaving sion with me. I thought it was ok, and with poppy out of the way, and sion not being a heavy damage dealer, i would trade with the sion until he was low (leaving me with around 500 hp,) until he would go into a bush, and form what i could assume, was going back. little did i know he was charging up his q and w to burst me down so he could finish me with ignite and ult away before i could do anything, leaving me with a grey screen. I want to know if it was riots purpose to make his q's windup invisible (i mean the indicators in front of sion showing where the effects take place) while he was in the bush, or if it is a bug that they were not aware of and are willing to fix/alter.

Any information regarding how this is supposed to work would be welcome. thx for your time.

(ps forgive any spelling/grammer misusage, english is not my first language.) :)