Ideally, yes, retaining the progress would be the best option.
But what objectives add 25 minutes? Are you sure you didn't already have time on the clock? You know that carries over, right? If you have 10 minutes when you finish an objective, and it adds another 15, you'll end up with 25 minutes for the next objective - but it still only added 15 minutes. What if when the host migrates, you reset to the base time for the objective as well as the 0% progress? - I mean, it's not ideal, but if they can't retain the progress for some reason, that WOULD be a better option than what happens now.
not sure about the 25 minutes, you may be right there.
yeah basically, the way its set up right now is about as bad as it could be for host migration... reset the objective and not the clock is a FAIL. so i agree, it would be much better to have the timer reset to the current objectives base time.
still, even if that were implemented, its kinda lame to think that you'd have to start over, when i'm sure its not impossible to migrate the objective status...
even the location of each player could be migrated so that you're literally continuing the match as it was when the host dropped out, rather than resetting everyone to their spawn.