It's the only guaranteed source of watchwork sprockets besides the home instance node, so there is already a reason to do it every day. Besides, they can always add an infusion to loot table to keep more people interested in it.
I don't think it needs to be nerfed. Encounter mechanics are extremely simple and consist of nothing more than basic gameplay knowledge such as not standing in red zones and using CC on enemies with a blue bar under their health bar. The only platform boss that might not be as obvious as the rest is lane 2 platform boss since it needs to be kited to mines to become vulnerable, but even that mechanic isn't exactly hard to figure out. The only change I would suggest is decreasing the duration of portal debuff, so in case it doesn't teleport any players to a platform, players from other lanes could go in and the event wouldn't fail due to a bug.
With all of that being said, I think the public version should definitely become a permanent option. I've done the private version 4 times and all of them have failed, with a few people flaming others and leaving the instance. On the other hand, out of the 18 public runs I've done I've lost only 2 of them, with one of those losses being on the first one available on EU, so I didn't mind it too much since there were probably plenty of people who haven't been around when the original event was going on so they weren't familiar with the encounter itself. Besides, it's been only a few days since the event was out and even then public runs are going pretty well. If public version would become permanent, more people would have the chance of getting familiar with the encounter and it would increase the success rate of the public version even more.