Hey Ownedcore!
I've noticed that the chances of spawning a Time-Lost Proto Drake are extremely high after a server reset, i've got my 4th Time-Lost Proto Drake this week.
As of what i have heard/read the chances of Vyragosa/Time-Lost has a 3-6 hour respawn. I've been camping Storm Peaks the 9 last weeks after a server reset and i've either found Vyragosa or Time-Lost spawning.
I hope this will help other people on their hunt!
Happy Hunting!