You are completely wrong here. The hunter casts misdirection in anticipation of his first attacks. As explained here the misdirection is then available for the next 30 seconds. The 4 second timer doesn't start until the first threat-generating attack by the hunter occurs.

So he has misdirection queued up, gives the tank 10 seconds to start their threat rotation (which is actually excessive) and then fires a multi-shot. Once the multi-shot is fired the threat is redirected to the tank. This hits multiple mobs and adds some low level threat to help the tank in case other DPS begin to AOE. He then fires his Explosive shot into the tank's target generating a large amount of threat for the tank.

At this point only 2 seconds has elapsed with the 1 sec GCD. He can then fire at least one more special shot (likely Arcane) into the tank's focus to increase that threat even higher. An autoshot or two will have also likely hit the tanks target and raise the threat even higher.

Now understand, at the point the 4 second misdirection threat redirection ends the tank has its own 10 seconds of threat generation, plus the 4 seconds of burst threat generated by the hunter, and the 4 seconds of threat the tank was able to generate for themselves while the hunter was misdirecting. The hunter has 0 threat at this point.

If the hunter is able to overtake the tank in threat at this point then it is clearly on the tank. From the story their gear is roughly the same level and hunters aren't crazy OP. The tank is either not doing their job correctly or there is a major issue with threat generation for druid tanks. I would point at the tank.