Multiple threads of splitting up the party can work when that is the way things have been designed (and can work better here than FtF, as demonstrated by our off time sblock's), but I'm under the impression that the distinct events upcoming (the secret DOOM, the blade show, etc.) are serial and non-overlapping in nature. I cannot say if Isida designed the upcoming secret DOOM to be only the four of you, but I know that I made sure Tondrek included everyone on his potential trip to Xen'drik because we are a party.
Trying to multiplex time does not really help the situation, and would make Isida's tasks more difficult as we have to keep track of what Bail is doing now and a month in the future, for example.
Perhaps it is just sblock burn out, but it is hard not to get the impression that this game is turning into the fab four and the occasional hangers on. I've tried to keep Tondrek involved, but with this secret, exclusive DOOM roadblock ahead, that is becoming more difficult. :\
I enjoy this game and I love Tondrek; that is way I'm dissapointed I do not actually get to play him.