No idea if this is an issue or not, but my friend and I have been trying to get the full vanguard set for the powerful engram quest, but the titan mark seems to be a super rare drop. I ground out strikes all evening and I got two helms, three guns, a shoulder piece and yet another chest piece (had four chests at one point). Is the titan mark even a drop from Zavalla? It feels rarer than an exotic at this point. If anyone has found one, please let us know as we are currently wondering if it's not dropping due to a bug. Might also affect other classes?