Quote Originally Posted by Krojack View Post
Sycrus Tower becomes required content for current 5.3 MSQ content.
It's actually required to finish 2.5 now. The MSQ won't let you progress into the final quests after the Steps of Faith if you haven't finished the Crystal Tower quests. There's even a short cutscene added when the Scions move to Mor Dhona in the first place to direct you towards it, although it doesn't make it mandatory until later.