How is that explainable or excusable? Not just referencing the block explorer now, anyone can go and see for themselves.
It is not important how fast bot can calculate the solution. The key is how optimal his solution will be. If bot can find a 20sec solution in 3 sec but can't find a 15 sec solution then it will lose to super human who can finish the level in 15sec. Difficulty threshold will do the trick.
We have two options:
1) Bots are stupid but fast then they will dominate for the next 2000-6000 blocks. Until threshold will lower and kick them off.
2) Bots are smart. Then humans are off the race.