Turbine have added many different events over the year. The first, and before my time was the devils invasion of the Marketplace and that later on was made into a raid via ‘time travel’. There was also some kind of climbing event in the asian server (vaguely remembering so I might be wrong).
The first event that I remember was Risia. Second Mabar. Later on when Eveningstar was added through MOTU we got Eveningstar winter games (or whatever it’s named) which is a different public spectacle unlike Risia but rolls out at the same time. Then we have Crystal Cove. Crystal Cove eventually lead to the Cannith challenges and also inspired Eveningstar challenges. Most of them with a similar theme.
The Mimic hunt comes as a result of Mabar adding so much lag to the servers (but lately Turbine have talked about bringing Mabar back in some way). The Mimic hunt is also a mix of the 8th anniversary system, mixing 2 random cards together for a reward, by turning in motes (a late addition to Mabar before they had to shut the event down).
So basically, when you look at all the events you realize how one part inspired the other and while some events comes and goes, parts of it is still a permanent staple of the DDO gameworld.
Now my suggestions is simply to keep the Mimic hunt. Maybe turn out the frenzy part off and just add a nice reward table based on Motes alone and not cards. No need to make the process convoluted in the long run. The reason is simple – it feels right. Running into Mimics is fun and surprising, and a far more eventful surprise than a bunch of black pudding champions. It feels like a reward; not only can chests that normally only hold keys and such be Mimics but anything – even end chests. Like the EH spinner that I did, where both chests at the end were part of a Mimic Frenzy going on. There I was, freshly done beating the Spinner and suddenly I had to deal with some Mimics.
Every time is a joy and in the long run I have the Motes to show for it. Just make that into a nice turn in.
Another event that can be made permanent is Crystal Cove. It’s separate from the public sphere and it’s more like a challenge anyways. I’d do it every life if I could and it would provide me with the opportunity to work up some of the gear but on my time table and not Turbines. I like the event; it just never runs when I feel like I have the interest or the time.