|Companion rewards for the event|
The D3 Season model is a good one. It encourages you to try a different character and focus on that character for a period of time. Instead of just having "max-level" as a goal, it breaks it up into sub-goals which are achievable, and which guide you through all the content.
If this had been the entirety of the event, I think it would have been received positively by the community. But Bioware had to include a top level "Legendary" tier which requires you to level all 8 classes, and do most of the content in the game.
The Legendary tier is quite clearly aimed at the super-hardcore, a challenge for them. But I think the bulk of the community took it badly. For one thing, most people don't have 8 character slots free, requiring them to buy more. As well, if you only have to level one character, you can choose a story which you haven't done yet, or would like to try a different path through. This choice would be different for each player.
In many ways, this is a case of addition through subtraction. If Bioware had simply cut the top tier entirely, this event would be far more appealing. As well, they could repeat it next year, and people could try a different story. For example, in D3, I do one class a season. This season was Witch Doctor, last season was Barbarian. Next season will probably be Demon Hunter.
The lesson here is that you don't always have to challenge the hardcore. For time-limited events in particular, perhaps it's better to have an event that the majority of players complete, rather than one where only a few players get to the end.