I think these events should be regularly happening events. Except not for sigil. Make the prizes more for helping you attain lineage dragons, ie more tokens. And other harder to acquire items such as rune dust and glyph prizes.
They could run these events along side other non pvp seasonal events or towards the end of any seasonal event. As many events get very long in the tooth towards the end of the week. I know I for one get tired of most events by like Sunday and get bored. That said I still participate and don’t think the events should be shortened (because many need the time to acquire the prizes they need for the season, myself included) but maybe these events could be either thrown in alongside these events (especially non pvp events) or be a mini event towards the end of one of the seasonal events to break up the boring ending of most events and give us something else to do. I would enjoy them if they were weekly but you could adjust it to less for sure.
Particularly Dragon games, I believe. I would like a reason to use all the old tier dragons more often.