Marketing wise it definitely pays to have 5 separate events to push your product compared to one.
Development wise it may be that Lennox is the only one that is complete, and the development schedule has, for whatever reason, been lined up so that work on each new character/monster is somewhat more sequential.
This could be because development time is split between more things whereas it was focused on T4 post-launch, or perhaps 2k/TRS are listening to the fact people love to moan on here about how there aren’t “enough updates” and this gives them the opportunity to have a more efficient workflow that also provides more regular “exciting” news.
As for releases… I’d be pleasantly surprised if the releases were finished before the middle of August, and that’s assuming that they do their usual gig of releasing updates once a fortnight. Until we get the release dates we won’t know, but it might be best for personal sanity reasons to not presume that this content is going to be completely with us before the summer ends. You know, managing expectations and all