I could go into a bunch of detail but I'm lazy.
The summer event was clearly the best. It had something for everyone to the point everyone spammed so much they burnt out. Only a few are still spamming. The idea of incorporating HBR into the mix, was a smart move which incorporates the ideal of ''you work hard and you gain''. Which is an ideal I like.
Easter while I enjoyed it we all know was a bit of a flop. With quests like PTS and WOF have stupid amounts of enemies it came down to people solo spamming the first room of WoF or Retraping 2 or 3 times in a PTS room (you know which I mean). It got boring fast though I had no personal gripe with NoLifing it as long as I wasn't soloing too much. Obviously these got taken down and for good reason.
I was too late for Christmas but from what I can tell was just fiasco release and presents? If i am wrong please inform me.
Fiasco being an event only quest is great, it keeps it fresh. For those who have played it, get to experience nostalgia amongst some fun slaughtering whilst newer players get the enjoyment of a spammy quest they gave never played.
Halloween I was not here to comment upon.
Something to mention that I haven't seen was that during April fools we had 'shadows' forest quest where we fought 'drak flaz' at the end. It was a very entertaining quest.