Absolutely -blam!- ridiculous. I was at the final boss (which is already a -blam!- as a solo Hunter) with a sliver of his health left and the -blam!- timer ran out. So obviously I was frustrated, but I figured it would send me to the last rally flag with the timer set where it was the first time BUT NO, I have to start over at the beginning of the -blam!- jumping section (which is awful) and do Ithe 4 light and dark blights section of the mission again. I just wasted 40+ minutes of the precious little time I have to play with nothing to show for it. Thanks Bungie. This is the sort of thing that makes people quit playing. Tl;dr: either the timer has got to go, or the checkpoints need to be more reasonable. Playing through 40 minutes of a mission with no ROI leaves a bad taste in your mouth.