The time limit is fine /most/ of the time for me
I have to do it first thing when I get on though and have no other programs running on my computer; otherwise the lag kills it

I remember the first time it came out it was impossible for me. It lagged so much that no matter how fast I completed one round, the timer would continue to run in the background during the little victory animation, and the timer would actually run out and say I failed before the second or third round ever even appeared. The completed casting animation completely kills any chance of winning if the client is running slow since the timer does not pause between rounds