Disagree completely with both of you completely. Watch the fight again, Vitor maybe lands 2/3 clean blows on the ground out of about 10 thrown, the rest he either misses completely or was absorbed by Bispings arms.
Obviously it differs from fight to fight, situation to situation, however in that case I'd have liked the referee to have just given it a few more seconds much like the referee of the Carwin/Lesnar fight. In both cases Bisping/Lesnar were badly hurt & both Bisping & Lesnar remained static for a few seconds, however in Lesnar's case seeing he was still protecting himself the referee gave him a warning to show him something which prompted him to react.
There's no doubt the head kick hurt Bisping, but he was still had enough wits to keep himself covered up meaning he obviously wasn't that out of it.